What is the define of your butt?

The Word 'butt' is both a noun (butt, butts) and a verb (butt, butts, butting, butted).

The noun 'butt' is a Word for a blow or thrust with the head or horns; a shortened form of the noun 'buttocks' (etymology dubious; "buttock" is thought to be derived from the noun "butt"); the thicker or bottom end of something; a used, extinguished cigarette; a target or object of a practical joke; a large cask.

The term 'your butt' refers to the buttocks of the person being spoken to.

The verb 'butt' is to hit someone or something with the head or horns; an action verb.