mortise Syllabification: (mor·tise)Pronunciation: /ˈmôrtis/ (also mortice)Definition of mortise noun a hole or recess cut into a part, designed to receive a corresponding projection (a tenon) on another part so as to join or lock the parts together. verb [with object] join securely by using a mortise and tenon. [with object] (often as adjective mortised) cut a mortise in or through:the mortised portsDerivatives mortiser noun Origin: late Middle English: from Old French mortaisemortise in other Oxford dictionaries Definition of mortise in the British & World English dictionary