The word ''revelation'' in Quran

Revelation should have some signs or should have means of expressing it.
Quran states
فَخَرَجَ عَلَىٰ قَوْمِهِ مِنَ الْمِحْرَابِ فَأَوْحَىٰ إِلَيْهِمْ أَن سَبِّحُوا بُكْرَةً وَعَشِيًّا
So Zakariya came out to his people from him chamber: He told them by signs to celebrate Allah´s praises in the morning and in the evening.
كَذَٰلِكَ جَعَلْنَا لِكُلِّ نَبِيٍّ عَدُوًّا شَيَاطِينَ الْإِنسِ وَالْجِنِّ يُوحِي بَعْضُهُمْ إِلَىٰ بَعْضٍ زُخْرُفَ الْقَوْلِ غُرُورًا ۚ وَلَوْ شَاءَ رَبُّكَ مَا فَعَلُوهُ ۖ فَذَرْهُمْ وَمَا يَفْتَرُونَ
Likewise did We make for every Messenger an enemy,- evil ones among men and jinns, inspiring each other with flowery discourses by way of deception. If thy Lord had so planned, they would not have done it: so leave them and their inventions alone.
وَلَا تَأْكُلُوا مِمَّا لَمْ يُذْكَرِ اسْمُ اللَّهِ عَلَيْهِ وَإِنَّهُ لَفِسْقٌ ۗ وَإِنَّ الشَّيَاطِينَ لَيُوحُونَ إِلَىٰ أَوْلِيَائِهِمْ لِيُجَادِلُوكُمْ ۖ وَإِنْ أَطَعْتُمُوهُمْ إِنَّكُمْ لَمُشْرِكُونَ
Eat not of (meats) on which Allah´s name hath not been pronounced: That would be impiety. But the evil ones ever inspire their friends to contend with you if ye were to obey them, ye would indeed be Pagans.
مِن شَرِّ الْوَسْوَاسِ الْخَنَّاسِ
From the mischief of the Whisperer (of Evil), who withdraws (after his whisper).
The prophet (peace of Allah be upon him and his descendants) states '' Satan has some good companions''.
Divine messages that are inculcated to prophets and Imams are called '' revelation''.
Quran states
وَمَا كَانَ لِبَشَرٍ أَن يُكَلِّمَهُ اللَّهُ إِلَّا وَحْيًا أَوْ مِن وَرَاءِ حِجَابٍ أَوْ يُرْسِلَ رَسُولًا فَيُوحِيَ بِإِذْنِهِ مَا يَشَاءُ ۚ إِنَّهُ عَلِيٌّ حَكِيمٌ
It is not fitting for a man that Allah should speak to him except by inspiration, or from behind a veil, or by the sending of a messenger to reveal, with Allah´s permission, what Allah wills: for He is Most High, Most Wise.
Gabriel came to the messenger of God (peace of Allah be upon him and his descendants) in a specific way. Or Hazrat Musa (peace be upon him) heard the remarks of God without seeing.
The remarks of God are inculcated as inspiration;
وَأَوْحَيْنَا إِلَىٰ أُمِّ مُوسَىٰ أَنْ أَرْضِعِيهِ ۖ فَإِذَا خِفْتِ عَلَيْهِ فَأَلْقِيهِ فِي الْيَمِّ وَلَا تَخَافِي وَلَا تَحْزَنِي ۖ إِنَّا رَادُّوهُ إِلَيْكِ وَجَاعِلُوهُ مِنَ الْمُرْسَلِينَ
So We sent this inspiration to the mother of Moses: "Suckle (thy child), but when thou hast fears about him, cast him into the river, but fear not nor grieve: for We shall restore him to thee, and We shall make him one of Our messengers''.
Or the remarks of God are inculcated as surrendering;
وَأَوْحَىٰ رَبُّكَ إِلَى النَّحْلِ أَنِ اتَّخِذِي مِنَ الْجِبَالِ بُيُوتًا وَمِنَ الشَّجَرِ وَمِمَّا يَعْرِشُونَ
And thy Lord taught the Bee to build its cells in hills, on trees, and in (men´s) habitations.
The prophet (peace of Allah be upon him and his descendants) stated '' divine messages disconnected, but annunciation remained''.
Dream of a believer, inspiration, surrendering and sleep that are expressed in Quran are called '' revelation''.
وَمَا كَانَ لِبَشَرٍ أَن يُكَلِّمَهُ اللَّهُ إِلَّا وَحْيًا أَوْ مِن وَرَاءِ حِجَابٍ أَوْ يُرْسِلَ رَسُولًا فَيُوحِيَ بِإِذْنِهِ مَا يَشَاءُ ۚ إِنَّهُ عَلِيٌّ حَكِيمٌ
It is not fitting for a man that Allah should speak to him except by inspiration, or from behind a veil, or by the sending of a messenger to reveal, with Allah´s permission, what Allah wills: for He is Most High, Most Wise.

فَاتَّخَذَتْ مِن دُونِهِمْ حِجَابًا فَأَرْسَلْنَا إِلَيْهَا رُوحَنَا فَتَمَثَّلَ لَهَا بَشَرًا سَوِيًّا
She placed a screen (to screen herself) from them; then We sent her our angel, and he appeared before her as a man in all respects.
Revelation of God includes prophets as well as other creatures such as plants and insects. It is related to situation of each thing in a specific place.
God has control of whatever God has created;
صِرَاطِ اللَّهِ الَّذِي لَهُ مَا فِي السَّمَاوَاتِ وَمَا فِي الْأَرْضِ ۗ أَلَا إِلَى اللَّهِ تَصِيرُ الْأُمُورُ
The Way of Allah, to Whom belongs whatever is in the heavens and whatever is on earth. Behold (how) all affairs tend towards Allah.
Quran states
زَلَ بِهِ الرُّوحُ الْأَمِينُ
With it came down the spirit of Faith and Truth.
قُلْ أَيُّ شَيْءٍ أَكْبَرُ شَهَادَةً ۖ قُلِ اللَّهُ ۖ شَهِيدٌ بَيْنِي وَبَيْنَكُمْ ۚ وَأُوحِيَ إِلَيَّ هَٰذَا الْقُرْآنُ لِأُنذِرَكُم بِهِ وَمَن بَلَغَ ۚ أَئِنَّكُمْ لَتَشْهَدُونَ أَنَّ مَعَ اللَّهِ آلِهَةً أُخْرَىٰ ۚ قُل لَّا أَشْهَدُ ۚ قُلْ إِنَّمَا هُوَ إِلَٰهٌ وَاحِدٌ وَإِنَّنِي بَرِيءٌ مِّمَّا تُشْرِكُونَ
Say: "What thing is most weighty in evidence?" Say: "Allah is witness between me and you; This Qur´an hath been revealed to me by inspiration, that I may warn you and all whom it reaches. Can ye possibly bear witness that besides Allah there is another Allah?" Say: "Nay! I cannot bear witness!" Say: "But in truth He is the one Allah, and I truly am innocent of (your blasphemy of) joining others with HimIt should be mentioned that some Sunni Scientists have mentioned one of meanings of divine messages as book and mission. Their purpose is whatever is descended from the sky or from the earth. Their purpose is heavenly books and missions of God from God to messengers and prophets so that they can transfer them to human.
وَلَقَدْ كُذِّبَتْ رُسُلٌ مِّن قَبْلِكَ فَصَبَرُوا عَلَىٰ مَا كُذِّبُوا وَأُوذُوا حَتَّىٰ أَتَاهُمْ نَصْرُنَا ۚ وَلَا مُبَدِّلَ لِكَلِمَاتِ اللَّهِ ۚ وَلَقَدْ جَاءَكَ مِن نَّبَإِ الْمُرْسَلِينَ
Rejected were the messengers before thee: with patience and constancy they bore their rejection and their wrongs, until Our aid did reach them: there is none that can alter the words (and decrees) of Allah. Already hast thou received some account of those messengers.
وَإِن كَانَ كَبُرَ عَلَيْكَ إِعْرَاضُهُمْ فَإِنِ اسْتَطَعْتَ أَن تَبْتَغِيَ نَفَقًا فِي الْأَرْضِ أَوْ سُلَّمًا فِي السَّمَاءِ فَتَأْتِيَهُم بِآيَةٍ ۚ وَلَوْ شَاءَ اللَّهُ لَجَمَعَهُمْ عَلَى الْهُدَىٰ ۚ فَلَا تَكُونَنَّ مِنَ الْجَاهِلِينَ
If their spurning is hard on thy mind, yet if thou wert able to seek a tunnel in the ground or a ladder to the skies and bring them a sign,- (what good?). If it were Allah´s will, He could gather them together unto true guidance: so be not thou amongst those who are swayed by ignorance (and impatience).
وَعِندَهُ مَفَاتِحُ الْغَيْبِ لَا يَعْلَمُهَا إِلَّا هُوَ ۚ وَيَعْلَمُ مَا فِي الْبَرِّ وَالْبَحْرِ ۚ وَمَا تَسْقُطُ مِن وَرَقَةٍ إِلَّا يَعْلَمُهَا وَلَا حَبَّةٍ فِي ظُلُمَاتِ الْأَرْضِ وَلَا رَطْبٍ وَلَا يَابِسٍ إِلَّا فِي كِتَابٍ مُّبِينٍ
With Him are the keys of the unseen, the treasures that none knoweth but He. He knoweth whatever there is on the earth and in the sea. Not a leaf doth fall but with His knowledge: there is not a grain in the darkness (or depths) of the earth, nor anything fresh or dry (green or withered), but is (inscribed) in a record clear (to those who can read).
وَذَرِ الَّذِينَ اتَّخَذُوا دِينَهُمْ لَعِبًا وَلَهْوًا وَغَرَّتْهُمُ الْحَيَاةُ الدُّنْيَا ۚ وَذَكِّرْ بِهِ أَن تُبْسَلَ نَفْسٌ بِمَا كَسَبَتْ لَيْسَ لَهَا مِن دُونِ اللَّهِ وَلِيٌّ وَلَا شَفِيعٌ وَإِن تَعْدِلْ كُلَّ عَدْلٍ لَّا يُؤْخَذْ مِنْهَا ۗ أُولَٰئِكَ الَّذِينَ أُبْسِلُوا بِمَا كَسَبُوا ۖ لَهُمْ شَرَابٌ مِّنْ حَمِيمٍ وَعَذَابٌ أَلِيمٌ بِمَا كَانُوا يَكْفُرُونَ
Leave alone those who take their religion to be mere play and amusement, and are deceived by the life of this world. But proclaim (to them) this (truth): that every soul delivers itself to ruin by its own acts: it will find for itself no protector or intercessor except Allah: if it offered every ransom, (or reparation), none will be accepted: such is (the end of) those who deliver themselves to ruin by their own acts: they will have for drink (only) boiling water, and for punishment, one most grievous: for they persisted in rejecting Allah.
وَحَاجَّهُ قَوْمُهُ ۚ قَالَ أَتُحَاجُّونِّي فِي اللَّهِ وَقَدْ هَدَانِ ۚ وَلَا أَخَافُ مَا تُشْرِكُونَ بِهِ إِلَّا أَن يَشَاءَ رَبِّي شَيْئًا ۗ وَسِعَ رَبِّي كُلَّ شَيْءٍ عِلْمًا ۗ أَفَلَا تَتَذَكَّرُونَ
His people disputed with him. He said: "(Come) ye to dispute with me, about Allah, when He (Himself) hath guided me? I fear not (the beings) ye associate with Allah: Unless my Lord willeth, (nothing can happen). My Lord comprehendeth in His knowledge all things. Will ye not (yourselves) be admonished?
وَهُوَ الَّذِي أَنزَلَ مِنَ السَّمَاءِ مَاءً فَأَخْرَجْنَا بِهِ نَبَاتَ كُلِّ شَيْءٍ فَأَخْرَجْنَا مِنْهُ خَضِرًا نُّخْرِجُ مِنْهُ حَبًّا مُّتَرَاكِبًا وَمِنَ النَّخْلِ مِن طَلْعِهَا قِنْوَانٌ دَانِيَةٌ وَجَنَّاتٍ مِّنْ أَعْنَابٍ وَالزَّيْتُونَ وَالرُّمَّانَ مُشْتَبِهًا وَغَيْرَ مُتَشَابِهٍ ۗ انظُرُوا إِلَىٰ ثَمَرِهِ إِذَا أَثْمَرَ وَيَنْعِهِ ۚ إِنَّ فِي ذَٰلِكُمْ لَآيَاتٍ لِّقَوْمٍ يُؤْمِنُونَ
It is He Who sendeth down rain from the skies: with it We produce vegetation of all kinds: from some We produce green (crops), out of which We produce grain, heaped up (at harvest); out of the date-palm and its sheaths (or spathes) (come) clusters of dates hanging low and near: and (then there are) gardens of grapes, and olives, and pomegranates, each similar (in kind) yet different (in variety): when they begin to bear fruit, feast your eyes with the fruit and the ripeness thereof. Behold! in these things there are signs for people who believe.
وَمَا لَكُمْ أَلَّا تَأْكُلُوا مِمَّا ذُكِرَ اسْمُ اللَّهِ عَلَيْهِ وَقَدْ فَصَّلَ لَكُم مَّا حَرَّمَ عَلَيْكُمْ إِلَّا مَا اضْطُرِرْتُمْ إِلَيْهِ ۗ وَإِنَّ كَثِيرًا لَّيُضِلُّونَ بِأَهْوَائِهِم بِغَيْرِ عِلْمٍ ۗ إِنَّ رَبَّكَ هُوَ أَعْلَمُ بِالْمُعْتَدِينَ
Why should ye not eat of (meats) on which Allah´s name hath been pronounced, when He hath explained to you in detail what is forbidden to you - except under compulsion of necessity? But many do mislead (men) by their appetites unchecked by knowledge. Thy Lord knoweth best those who transgress.
وَإِذَا جَاءَتْهُمْ آيَةٌ قَالُوا لَن نُّؤْمِنَ حَتَّىٰ نُؤْتَىٰ مِثْلَ مَا أُوتِيَ رُسُلُ اللَّهِ ۘ اللَّهُ أَعْلَمُ حَيْثُ يَجْعَلُ رِسَالَتَهُ ۗ سَيُصِيبُ الَّذِينَ أَجْرَمُوا صَغَارٌ عِندَ اللَّهِ وَعَذَابٌ شَدِيدٌ بِمَا كَانُوا يَمْكُرُونَ
When there comes to them a sign (from Allah), They say: "We shall not believe until we receive one (exactly) like those received by Allah´s messengers." Allah knoweth best where (and how) to carry out His mission. Soon will the wicked be overtaken by humiliation before Allah, and a severe punishment, for all their plots.
وَيَوْمَ يَحْشُرُهُمْ جَمِيعًا يَا مَعْشَرَ الْجِنِّ قَدِ اسْتَكْثَرْتُم مِّنَ الْإِنسِ ۖ وَقَالَ أَوْلِيَاؤُهُم مِّنَ الْإِنسِ رَبَّنَا اسْتَمْتَعَ بَعْضُنَا بِبَعْضٍ وَبَلَغْنَا أَجَلَنَا الَّذِي أَجَّلْتَ لَنَا ۚ قَالَ النَّارُ مَثْوَاكُمْ خَالِدِينَ فِيهَا إِلَّا مَا شَاءَ اللَّهُ ۗ إِنَّ رَبَّكَ حَكِيمٌ عَلِيمٌ
One day will He gather them all together, (and say): "O ye assembly of Jinns! Much (toll) did ye take of men." Their friends amongst men will say: "Our Lord! we made profit from each other: but (alas!) we reached our term - which thou didst appoint for us." He will say: "The Fire be your dwelling-place: you will dwell therein for ever, except as Allah willeth." for thy Lord is full of wisdom and knowledge.
يَا مَعْشَرَ الْجِنِّ وَالْإِنسِ أَلَمْ يَأْتِكُمْ رُسُلٌ مِّنكُمْ يَقُصُّونَ عَلَيْكُمْ آيَاتِي وَيُنذِرُونَكُمْ لِقَاءَ يَوْمِكُمْ هَٰذَا ۚ قَالُوا شَهِدْنَا عَلَىٰ أَنفُسِنَا ۖ وَغَرَّتْهُمُ الْحَيَاةُ الدُّنْيَا وَشَهِدُوا عَلَىٰ أَنفُسِهِمْ أَنَّهُمْ كَانُوا كَافِرِينَ
O ye assembly of Jinns and men! came there not unto you messengers from amongst you, setting forth unto you My signs, and warning you of the meeting of this Day of yours?" They will say: "We bear witness against ourselves." It was the life of this world that deceived them. So against themselves will they bear witness that they rejected Faith.
وَقَالُوا هَٰذِهِ أَنْعَامٌ وَحَرْثٌ حِجْرٌ لَّا يَطْعَمُهَا إِلَّا مَن نَّشَاءُ بِزَعْمِهِمْ وَأَنْعَامٌ حُرِّمَتْ ظُهُورُهَا وَأَنْعَامٌ لَّا يَذْكُرُونَ اسْمَ اللَّهِ عَلَيْهَا افْتِرَاءً عَلَيْهِ ۚ سَيَجْزِيهِم بِمَا كَانُوا يَفْتَرُونَ
And they say that such and such cattle and crops are taboo, and none should eat of them except those whom - so they say - We wish; further, there are cattle forbidden to yoke or burden, and cattle on which, (at slaughter), the name of Allah is not pronounced; - inventions against Allah´s name: soon will He requite them for their inventions.
قَدْ خَسِرَ الَّذِينَ قَتَلُوا أَوْلَادَهُمْ سَفَهًا بِغَيْرِ عِلْمٍ وَحَرَّمُوا مَا رَزَقَهُمُ اللَّهُ افْتِرَاءً عَلَى اللَّهِ ۚ قَدْ ضَلُّوا وَمَا كَانُوا مُهْتَدِينَ
Lost are those who slay their children, from folly, without knowledge, and forbid food which Allah hath provided for them, inventing (lies) against Allah. They have indeed gone astray and heeded no guidance.
Imam Ali (peace be upon him) states about Quran '' its wonders are endless''.