compensator

Short definition from Wiktionary

Noun

1. 1
   A party or thing which compensates, pays or otherwise provides a compensation
2. 2
   Any device used to compensate for something, notably to achieve a better balance.
3. 3
   A building control device used to deliver the compensation relationship or curve between the air temperature outside a building and the temperature of water or air provided to spaces or zones within the building for purposes of heating or cooling.
4. 4
   One of several small magnets placed in the binnacle to neutralize the effect of the ship's metal on the compass