Available Definitions:
1) n. - A cavity cut into a piece of timber, or other material, to receive something (as the end of another piece) made to fit it, and called a tenon.
2) v. t. - To cut or make a mortisein.
3) v. t. - To join or fasten by a tenon and mortise; as, to mortise a beam into a post, or a joist into a girder.