Sometimes, you sit on a chair has 1 leg or 2 legs a bit shorter than the others. You can push your body back and forward to rock the chair side to side, which makes it hard for you to sit because you can't sit stably on it.
So, do we say "the chair is uneven"?
I have found this word, but I am not sure if native people say "the chair is wobbly"
wobbly (adj): not properly fixed in place so that it moves from side to side
a chair with a wobbly leg
a wobbly tooth