Verb

1. To cut or divide into two parts.
2. To divide an angle, line segment, or other figure into two equal parts.

Noun

1. A bisector, which divides into two equal parts.
2. An envelope, card, or fragment thereof showing an affixed cut half of a regular issued stamp, over which one or more postal markings have been applied. Typically used in wartime when normal lower rate stamps may not be available.