When the term mitre is used in reference to lap joints, this is a highly technical use of the term typically only exchanged amongst professional woodworkers. The most likely use of the term is going to be in conjunction with a saw. If this is the case, then mitre can refer to the jig into which a flat saw is inserted to assist in cutting precise angles every time. Most professionals no use electric powered mitre saws that consist of circular saw blade attached to a spring returned arm that is pulled downward to introduce the cut to the wood. This should not be confused with a radial arm saw though both can be used for accomplishing similar styles of cutting.