When you debunk something you show it to be false. For over a century people have tried to debunk the notion of natural selection, but no one has succeeded. It's a very hard idea to debunk.
To debunk something is to prove it wrong. The idea that music education is frivolous and should be the first item cut from the budget was long ago debunked: in schools with strong music programs, students always do better. Columbus debunked the idea that the world was flat: he showed clearly that it was round.
