damper

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One that deadens, restrains, or depresses.
• noun An adjustable plate, as in the flue of a furnace or stove, for controlling the draft.
• noun A device in various keyboard instruments for deadening the vibrations of the strings.
• noun A mute for various brass instruments.
• noun A device that eliminates or diminishes vibrations or oscillations, as of a magnetic needle.

from The Century Dictionary.

• noun One who or that which damps.
• noun A kind of unfermented bread, made of flour and water, and generally baked on a stone.

from the GNU version of the Collaborative International Dictionary of English.

• noun 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.
• noun A contrivance, as in a pianoforte, to deaden vibrations; or, as in other pieces of mechanism, to check some action at a particular time.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Something that damps or checks:
• noun Bread made from a basic recipe of flour, water, milk, and salt, but without yeast.
• adjective comparative form of damp: more damp

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a device that decreases the amplitude of electronic, mechanical, acoustical, or aerodynamic oscillations
• noun a movable iron plate that regulates the draft in a stove or chimney or furnace
• noun a depressing restraint