Off-kilter is a term that describes something that is unbalanced or not quite right. The word can be used to describe a person's mental state, a physical object, or a situation that feels out of sync. The antonyms for off-kilter depend on the context in which the word is used. For instance, if off-kilter refers to a physical object, the antonyms can be balanced, stable, or even. If off-kilter describes a person's mental state, the antonyms can be calm, steady, or composed. In whatever context, the antonyms for off-kilter generally imply a sense of equilibrium or standard that has been met.