The Bible has a HUGE amount to say on this issue.
"For false christs and false prophets will arise and perform great signs and wonders, so as to lead astray, if possible, even the elect." Matt 24:24
" For the time is coming when people will not endure sound teaching, but having itching ears they will accumulate for themselves teachers to suit their own passions, 4 and will turn away from listening to the truth and wander off into myths." 2 Tim. 4:3-4
"And count the patience of our Lord as salvation, just as our beloved brother Paul also wrote to you according to the wisdom given him, 16 as he does in all his letters when he speaks in them of these matters. There are some things in them that are hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other Scriptures. 17 You therefore, beloved, knowing this beforehand, take care that you are not carried away with the error of lawless people and lose your own stability." 2 Peter 3:15-17
"Beloved, do not believe every spirit, but test the spirits to see whether they are from God, for many false prophets have gone out into the world. 2 By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God, 3 and every spirit that does not confess Jesus is not from God. This is the spirit of the antichrist, which you heard was coming and now is in the world already. 4 Little children, you are from God and have overcome them, for he who is in you is greater than he who is in the world.5 They are from the world; therefore they speak from the world, and the world listens to them. 6 We are from God. Whoever knows God listens to us; whoever is not from God does not listen to us. By this we know the Spirit of truth and the spirit of error." 1 John 4:16
"For there are many who are insubordinate, empty talkers and deceivers, especially those of the circumcision party. 11 They must be silenced, since they are upsetting whole families by teaching for shameful gain what they ought not to teach. 12 One of the Cretans, a prophet of their own, said, “Cretans are always liars, evil beasts, lazy gluttons.” 13 This testimony is true. Therefore rebuke them sharply, that they may be sound in the faith, 14 not devoting themselves to Jewish myths and the commands of people who turn away from the truth." Titus 1:10-14
"But false prophets also arose among the people, just as there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Master who bought them, bringing upon themselves swift destruction. 2 And many will follow their sensuality, and because of them the way of truth will be blasphemed. 3 And in their greed they will exploit you with false words. Their condemnation from long ago is not idle, and their destruction is not asleep....14They have eyes full of adultery, insatiable for sin. They entice unsteady souls. They have hearts trained in greed. Accursed children!...18 For, speaking loud boasts of folly, they entice by sensual passions of the flesh those who are barely escaping from those who live in error. 19 They promise them freedom, but they themselves are slaves of corruption. For whatever overcomes a person, to that he is enslaved." 2 Peter 2:1-3, 14, 18-19
The OT has a lot more on false prophets, too! Basically, anyone who preaches comfort and that God is pleased with them. Here is only a few of the verses I noted reading Jeremiah, just before Israel was taken into captivity to Babylon for apostasy and worshiping false Gods.
"An appalling and horrible thing
has happened in the land:
31 the prophets prophesy falsely,
and the priests rule at their direction;
my people love to have it so,
but what will you do when the end comes?" Jer. 5:30-31
" Then I said: “Ah, Lord God, behold, the prophets say to them, ‘You shall not see the sword, nor shall you have famine, but I will give you assured peace in this place.’” 14 And the Lord said to me: “The prophets are prophesying lies in my name. I did not send them, nor did I command them or speak to them. They are prophesying to you a lying vision, worthless divination, and the deceit of their own minds.15 Therefore thus says the Lord concerning the prophets who prophesy in my name although I did not send them, and who say, ‘Sword and famine shall not come upon this land’: By sword and famine those prophets shall be consumed." Jer. 14:13-15
"“I did not send the prophets,[FONT="][FONT="] yet they ran;
I did not speak to them,
yet they prophesied.
22 But if they had stood in my council,
then they would have proclaimed my words to my people,
and they would have turned them from their evil way,
and from the evil of their deeds.[/FONT]
[/FONT]
[FONT="]23 “Am I a God at hand, declares the Lord, and not a God far away?24 Can a man hide himself in secret places so that I cannot see him? declares the Lord. Do I not fill heaven and earth? declares the Lord.25 I have heard what the prophets have said who prophesy lies in my name, saying, ‘I have dreamed, I have dreamed!’" Jer. 23:21-25[/FONT]
So, a lot of definitions and this also shows us, that heresy is not unique to today.
Matt 24:24 - false teachers - perform signs and wonders
2 Tim. 4:3-4 teachers looking for people with "itching ears." Teachers who appeal to the flesh and passions.
2 Peter 3:15-17 ignorant and unstable twist Paul's writings to their own destruction. Lawless people!
1 John 4:16 - do not acknowledge Jesus Christ has come in the flesh.
Titus 1:10-14 Circumcision party - devoting themselves to Jewish myths
2 Peter 14 - false teachers who have eyes full of adultery, insatiable for sin, enticing unsteady souls, hearts trained in greed. (All the prosperity teachers??)
Jeremiah - prophecy lies saying everything is fine, when destruction is coming. (Specific to Israel or ?) Those who claim to "have a dream" and it is not from God.
So, lots of popular teachers could fit under these categories, especially greed. And Hebrew Roots, if it is taking people away from Jesus, people who deny Jesus came in the flesh, and I think people claiming to be gods, since they don't know who Jesus is, nor the responsibilities and burdens of God.