It means that something's just not right. Off balance. It's not all there.
She suddenly started laughing for no reason. She's a bit off kilter..
The definition of this word is in and of itself not "on kilter". I thought I would use symbols like " and "" ... you see.. that is two of them there. Please ask yourself... am I really reading something that someone just types for little to no reason? Then forget you asked that and carry on. Be good. Or. Well, just be good until we talk. Sometime.
For example, I really think I am off kilter after a couple mexican lunches in the can. You know? You better know. I am nean ... sorry I meant to spell "mean"... but I spelled it "nean".. my bad. Anyway. This is a good example.