*equalizer*

n. 1. One who, or that which, equalizes anything. [ 1913 Webster ]

2. same as Equalizing bar. [ Webster 1913 Suppl. ]

3. A device, as a bar, for operating two brakes, esp. a pair of hub brakes for an automobile, with equal force. [ Webster 1913 Suppl. ]

4. (Elec.) Any device for equalizing the pull of electromagnets; also, a conductor of low resistance joining the armature ends of the series field coils of dynamos connected in parallel. [ Webster 1913 Suppl. ]

5. (Aëronautics) A sliding panel to preserve the lateral stability of an aëroplane. [ Webster 1913 Suppl. ]

6. (Electronics) a device or circuit within a sound-reproducing system that reproduces the original frequency distribution of the sound before recording by compensating for inequialities in the frequency response of the system. [ PJC ]

7. a gun. [ slang ] [ PJC ]