...assonance. Or do. They're kinda interesting, actually. And I've used them to "cheat" in the past when writing poetry, although to tell the truth I don't care much for reading them in poetry. But what I dislike even more is the in- spelling-only rhyme, which I see most often in church songs, and I'm sorry to say I don't know the correct term for it. I can't even think of a good example right now, so nevermind. Actually, how about "lead" and "tread".
Where did I learn about assonance? It was in CS Lewis' The Voyage of the Dawn Treader, of course. Eustace tries to make up a limerick that pairs Narnia with balmier, and Lucy objects. Personally, I don't blame her.