(1):

(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.

(2):

(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.

(3):

(v. t.) To cut or make a mortisein.