kickback

from The American Heritage® Dictionary of the English Language, 5th Edition.

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

from the GNU version of the Collaborative International Dictionary of English.

• noun recoil, of a gun or machine, as in older automobile engines when started by turning a crank.
• noun 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
• transitive verb To pay (a kickback).
• intransitive verb To recoil; -- of guns and machines.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun countable A clandestine payment in return for a favor; especially an illegal one
• noun uncountable, firearms, machinery Recoil; a sudden backward motion, usually in the direction of the operator.
• noun 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
• noun oil industry A dangerous buildup of gas pressure at the wellhead
• noun countable, bowling The board separating one bowling lane from another at the pit end
• noun uncountable, bridge In contract bridge, an ace asking convention initiated by the first step above four of the agreed trump suit.
• noun pinball A feature that saves the ball from draining and propels it back into play.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb pay a kickback; make an illegal payment
• verb spring back, as from a forceful thrust
• noun a commercial bribe paid by a seller to a purchasing agent in order to induce the agent to enter into the transaction