kickback

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A sharp reaction; a repercussion.
2. n. Slang A return of a percentage of a sum of money already received, typically as a result of pressure, coercion, or a secret agreement.

Wiktionary

1. n. countable A clandestine payment in return for a favor; especially an illegal one
2. n. uncountable, firearms, machinery Recoil; a sudden backward motion, usually in the direction of the operator.
3. n. countable, machinery An accident wherein an object being cut by a rotating blade or disk, such as a circular saw, is caught by the blade and thrown outward
4. n. oil industry A dangerous buildup of gas pressure at the wellhead
5. n. countable, bowling The board separating one bowling lane from another at the pit end
6. n. uncountable, bridge In contract bridge, an ace asking convention initiated by the first step above four of the agreed trump suit.
7. n. pinball A feature that saves the ball from draining and propels it back into play.

GNU Webster's 1913

1. n. recoil, of a gun or machine, as in older automobile engines when started by turning a crank.
2. n. A secret, and usually illegal, payment, by a recipient of money paid for goods or services, to a facilitator of the transaction, of a portion of that money any portion of a gain made by the seller in a commercial transaction which is returned surreptitiously and illegally to a person (such as a purchasing agent) who authorized or recommended the purchase. It is generally considered a form of bribe.
3. v. To recoil; -- of guns and machines.
4. v. To pay (a kickback).

WordNet 3.0

1. v. pay a kickback; make an illegal payment
2. v. spring back, as from a forceful thrust
3. n. a commercial bribe paid by a seller to a purchasing agent in order to induce the agent to enter into the transaction