mitre

noun

1. A covering for the head, worn on solemn occasions by church dignitaries, which has been made in many forms, mostly recently a tall cap with two points or peaks.
2. The surface forming the bevelled end or edge of a piece where a miter joint is made; also, a joint formed or a junction effected by two beveled ends or edges; a miter joint.
3. (historical)A 13th-century coin minted in Europe which circulated in Ireland as a debased counterfeit sterling penny, outlawed under Edward I.
4. A cap or cowl for a chimney or ventilation pipe.
5. A gusset in sewing, etc.
6. (rare)A square with one triangular quarter missing from the outside.
7. A mitre shell

verb

1. (Commonwealth)To adorn with a mitre.
2. (Commonwealth)To unite at an angle of 45°.