The Collaborative International Dictionary of English v.0.48:

Gas \Gas\ (g[a^]s), v. t. [imp. & p. p. Gassed (g[a^]st); p.
   pr. & vb. n. Gassing.]
   1. (Textiles) To singe, as in a gas flame, so as to remove
      loose fibers; as, to gas thread.
      [Webster 1913 Suppl.]

   2. To impregnate with gas; as, to gas lime with chlorine in
      the manufacture of bleaching powder.
      [Webster 1913 Suppl.]

   3. to expose to a poisonous or noxious gas "The protest
      threatened to become violent, and the police gassed the
      demonstrators to force them to disperse."
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Gassing \Gas"sing\, n.
   1. (Manuf.) The process of passing cotton goods between two
      rollers and exposing them to numerous minute jets of gas
      to burn off the small fibers; any similar process of
      singeing.
      [1913 Webster]

   2. Boasting; insincere or empty talk. [Slang]
      [1913 Webster]

WordNet (r) 3.0 (2006):

gassing
    n 1: the process of interacting with gas
    2: the deliberate act of poisoning some person or animal with
       gas