1) American slang for to relax 2) American slang for a bribe 
Kick back is American slang for to relax.
[v] - pay a kickback 2. [v] - spring back, as from a forceful thrust
recoil verb spring back, as from a forceful thrust; `The gun kicked back into my shoulder`
[Logging] A strong thrust of the saw back toward the faller generally resulting from improper use of the nose of the bar or the pinching of the bar in a cut. Kickback causes loss of control of the saw and this in turn results in numerous saw cuts each year. Kick-back also refers to a tree jumping back over the stump toward t...