miter joint

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A joint made by beveling each of two surfaces to be joined, usually at a 45° angle, to form a corner, usually a 90° angle.

Wiktionary

1. n. A joint between two members at an angle to each other; each member is cut at an angle equal to half the angle of the junction and usually joint at right angles to each other.

GNU Webster's 1913

1. n. a joint formed by pieces matched and united upon a line bisecting the angle of junction, as by the beveled ends of two pieces of molding or brass rule, etc. The term is used especially when the pieces form a right angle, such as the edges of a window frame, and the edge of each piece at the point of junction is cut at a 45° angle to its long direction. See Miter, 2.

WordNet 3.0

1. n. joint that forms a corner; usually both sides are bevelled at a 45-degree angle to form a 90-degree corner