swap

Short definition from Wiktionary

Verb

1. 1
   To exchange or give (something) in an non-normal exchange (for something else).
2. 2
   To hit, to strike.
3. 3
   To beat the air, or ply the wings, with a sweeping motion or noise; to flap.
4. 4
   To descend or fall; to rush hastily or violently.

Noun

1. 1
   An exchange of two comparable things.
2. 2
   A financial derivative in which two parties agree to exchange one stream of non-normal cashflow against another stream.
3. 3
   Space available in a swap file for use as auxiliary memory.
4. 4
   A social meal at a restaurant between two university societies, usually involving drinking and banter; commonly associated with fining and pennying; equivalent to a crewdate at Oxford University.
5. 5
   A blow; a stroke.