damp

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

• adjective Slightly wet.
• adjective Humid.
• adjective Archaic Dejected; depressed.
• noun Moisture in the air; humidity.
• noun Moisture that lies or has condensed on something.
• noun Foul or poisonous gas that sometimes pollutes the air in coal mines.
• noun Lowness of spirits; depression.
• noun A restraint or check; a discouragement.
• transitive verb To make damp or moist; moisten.
• transitive verb To suppress or extinguish (a fire) by reducing or cutting off air.
• transitive verb To restrain or check; discourage.
• transitive verb Music To slow or stop the vibrations of (the strings of a keyboard instrument) with a damper.
• transitive verb Physics To decrease the amplitude of (an oscillating system).

from The Century Dictionary.

• noun Moist air; humidity; moisture.
• noun A poisonous vapor; specifically, in mining, a stifling or poisonous gas. See black-damp, fire-damp.
• noun A fog.
• noun A check; a discouragement.
• noun Depression of spirits; dejection.
• Moist; humid; moderately wet: as, a damp cloth; damp air.
• Clammy.
• Dejected; depressed.
• Synonyms Humid, Dank, etc. See moist.
• To moisten; make humid or moderately wet; dampen.
• To extinguish; smother; suffocate.
• To suffocate with damp or foul air in a mine. [Eng.]
• To check or retard the force or action of: as, to damp a fire by covering it with ashes; especially, to diminish the range or amplitude of vibrations in, as a piano-string, by causing a resistance to the motions of the vibrating body.
• To make dull or weak and indistinct, as a sound or a light; obscure; deaden.
• To depress; deject; discourage; deaden; check; weaken.
• Specifically To diminish or destroy the oscillation of (a metallic body in motion in a magnetic field).
• [Dampen is now more common in the literal sense, and is sometimes used in the derived senses.]
• Synonyms To moderate, allay, dispirit.
• In horticulture, to rot or waste away, as the stems and leaves of seedlings and other tender plants, when the soil and atmosphere in which they are vegetating are too wet or cold: with off: as, flower-seedlings in hotbeds are especially liable to damp off.
• noun The popular name of a disease which attacks young seedlings and succulent plants, causing them to rot off near the surface of the ground.

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

• noun Moisture; humidity; fog; fogginess; vapor.
• noun Dejection; depression; cloud of the mind.
• noun (Mining) A gaseous product, formed in coal mines, old wells, pints, etc.
• noun a damp consisting principally of carbonic acid gas; -- so called from its extinguishing flame and animal life. See Carbonic acid, under Carbonic.
• noun a curtain in a mine gallery to direct air currents and prevent accumulation of gas.
• noun a damp consisting chiefly of light carbureted hydrogen; -- so called from its tendence to explode when mixed with atmospheric air and brought into contact with flame.
• adjective Being in a state between dry and wet; moderately wet; moist; humid.
• adjective rare Dejected; depressed; sunk.
• intransitive verb To render damp; to moisten; to make humid, or moderately wet; to dampen.
• intransitive verb To put out, as fire; to depress or deject; to deaden; to cloud; to check or restrain, as action or vigor; to make dull; to weaken; to discourage.

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

• adjective Being in a state between dry and wet; moderately wet; moist.
• adjective obsolete Pertaining to or affected by noxious vapours; dejected, stupified.
• noun Moisture; humidity; dampness.
• noun archaic Fog; fogginess; vapor.