Damper n. : That which damps or checks; as: (a) A valve or movable plate in the flue or other part of a stove, furnace, etc., used to check or regulate the draught of air. (b) A contrivance, as in a pianoforte, to deaden vibrations; or, as in other pieces of mechanism, to check some action at a particular time.

Example:
How does the fresh air Damper feature of a thermostat work?

Taxonomy
Tuned mass damper, free encyclopedia, mechanical device, vibrations, mute, music, search, free dictionary, depresses, British, kinetic energy, absorb, energy peaks, normally generated, inductive, circuitry, deadening, HVAC terminology.

Defination from the web:
Damper (mast), a device that damps oscillation in radio masts and towers for better protection against storms. Tuned mass damper, a device mounted in structures to prevent discomfort, damage or structural failure by vibration ...