Swap

1. To strike; -- with off.
2. To fall or descend; to rush hastily or violently.
3. An exchange; a barter.
4. A blow; a stroke.
5. Hastily.
6. To exchange (usually two things of the same kind); to swop.
7. To beat the air, or ply the wings, with a sweeping motion or noise; to flap.