The heart of the word seems to be one of a change of mind, a turning away from. But the implication is that someone who turns away from something isn't going to jump back into the very thing he turned away from.
I hearkened and heard, but they spake not aright: no man repented him of his wickedness, saying, What have I done? every one turned to his course, as the horse rusheth into the battle.
Jeremiah 8:6
And just in the book of Jeremiah alone (the OT book in which the word appears most often), there are 10 verses where God is saying that He repents of something. Here are just a couple :
Thou hast forsaken me, saith the Lord, thou art gone backward: therefore will I stretch out my hand against thee, and destroy thee; I am weary with repenting.
Jeremiah 15:6
If that nation, against whom I have pronounced, turn from their evil, I will repent of the evil that I thought to do unto them.
Jeremiah 18:8
God is clearly saying He changed His mind - not that He stopped doing something.
So when you get to Paul's words in Romans 7 about wanting to do good but not finding the way to so do, you can't say that there isn't repentance there but rather the recognition of something deep that needs to be fundamentally changed before desire and behavior can line up. To define repentance simply as stop doing that is to make obedience to the law a prerequisite rather than an outcome. You really think if someone approached God and said something to the affect of "I can't stop doing this thing that I hate" that God would turn them away because they hadn't actually stopped doing it? Jesus came saying If thou wilt believe, not If thou wilt do.