The additional collateral given to liquidators as an incentive to perform liquidation of underwater accounts. For example, if the liquidation incentive is 1.1, liquidators receive an extra 10% of the borrowers collateral for every unit they close.
Unitroller
function liquidationIncentiveMantissa() view returns (uint)
RETURN: The liquidationIncentive, scaled by 1e18, is multiplied by the closed borrow amount from the liquidator to determine how much collateral can be seized.