I think the Scriptures do provide very specific descriptions of what a prophet is and how that prophet receives information from God (and how they do not!).
Below is a fairly extensive, but not comprehensive, list of verses pertaining to this subject. Notice that in almost every one of these descriptions of the prophet's call, one of three things happens:
1. The prophet has a powerful vision and SEES a vision of heaven or of the throne of God and is spoken to directly through that vision.
2. The prophet has a powerful dream in which God SPEAKS to them, revealing God's plan for the people.
3. The prophet HEARS an audible voice that is unmistakeable. In fact, Samuel thought someone was calling him and needed another prophet to inform him that it was the Lord. Also, the "man of God" received a very specific and direct word from God that was so specific that God killed him via a lion for not leaving immediately after his prophecy.
Also, notice that in these definitions of what a true prophet is and what a false prophet is, we see the following:
1. A true prophet actually hears/sees a message from God. A false prophet prophesies out of their imagination.
2. A true prophet's words are specific and will come to pass. A false prophet's predictions often are not and do not.
3. God's messages to the prophets were "secrets" or revelations that were not known to others. God revealed his hidden plans and purpose through them.
As a result of these very poignant and incredibly descriptive texts, I think it is clear that a prophet is one who has a heavenly vision, is spoken to in a dream, or hears an audible voice from God that reveals God's secrets and undisclosed revelations for his people concerning specific, upcoming events.
A prophet is NOT someone who speaks from their own spirit or presumes words from their own imaginations or impressions. Rather, these qualities are used to describe a false prophet.
Please see the texts below and make your own judgement concerning the definitions and descriptions of these prophet's roles and how they received their messages....
“And he said, “Hear my words: If there is a prophet among you, I the Lord make myself known to him in a vision; I speak with him in a dream.” (Numbers 12:6, ESV)
“But the prophet who presumes to speak a word in my name that I have not commanded him to speak, or who speaks in the name of other gods, that same prophet shall die.’ And if you say in your heart, ‘How may we know the word that the Lord has not spoken?’— when a prophet speaks in the name of the Lord, if the word does not come to pass or come true, that is a word that the Lord has not spoken; the prophet has spoken it presumptuously. You need not be afraid of him.” (Deuteronomy 18:20–22, ESV)
“And the Lord called Samuel again the third time. And he arose and went to Eli and said, “Here I am, for you called me.” Then Eli perceived that the Lord was calling the boy. Therefore Eli said to Samuel, “Go, lie down, and if he calls you, you shall say, ‘Speak, Lord, for your servant hears.’ ” So Samuel went and lay down in his place.” (1 Samuel 3:8–9, ESV)
“And as they sat at the table, the word of the Lord came to the prophet who had brought him back. And he cried to the man of God who came from Judah, “Thus says the Lord, ‘Because you have disobeyed the word of the Lord and have not kept the command that the Lord your God commanded you, but have come back and have eaten bread and drunk water in the place of which he said to you, “Eat no bread and drink no water,” your body shall not come to the tomb of your fathers.’ ” And after he had eaten bread and drunk, he saddled the donkey for the prophet whom he had brought back. And as he went away a lion met him on the road and killed him. And his body was thrown in the road, and the donkey stood beside it; the lion also stood beside the body.” (1 Kings 13:20–24, ESV)
“Where there is no prophetic vision the people cast off restraint, but blessed is he who keeps the law.” (Proverbs 29:18, ESV)