Source : Webster's Revised Unabridged Dictionary (1913)

Damp \Damp\ (d[a^]mp), n. [Akin to LG., D., & Dan. damp vapor,
   steam, fog, G. dampf, Icel. dampi, Sw. damb dust, and to MNG.
   dimpfen to smoke, imp. dampf.]
   1. Moisture; humidity; fog; fogginess; vapor.

            Night . . . with black air Accompanied, with damps
            and dreadful gloom.                   --Milton.

   2. Dejection; depression; cloud of the mind.

            Even now, while thus I stand blest in thy presence,
            A secret damp of grief comes o'er my soul.
                                                  --Addison.

            It must have thrown a damp over your autumn
            excursion.                            --J. D.
                                                  Forbes.

   3. (Mining) A gaseous product, formed in coal mines, old
      wells, pints, etc.

   {Choke damp}, a damp consisting principally of carbonic acid
      gas; -- so called from its extinguishing flame and animal
      life. See {Carbonic acid}, under {Carbonic}.

   {Damp sheet}, a curtain in a mine gallery to direct air
      currents and prevent accumulation of gas.

   {Fire damp}, 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.