a hole or recess cut into a part which is designed to receive a corresponding projection (a tenon) on another part so as to join or lock the parts together
榫孔,榫眼。
join securely by using a mortise and tenon
用榫舌榫眼连接。
[with  obj.][often  as adj. 
开榫眼
- 
                                                
the mortised ports .开了榫眼的舷窗。
 
"late Middle English: from Old French