Source : Webster's Revised Unabridged Dictionary (1913)

Laughing \Laugh"ing\, a. & n.
   from {Laugh}, v. i.

   {Laughing falcon} (Zo["o]l.), a South American hawk
      ({Herpetotheres cachinnans}); -- so called from its notes,
      which resemble a shrill laughing.

   {Laughing gas} (Chem.), hyponitrous oxide, or protoxide of
      nitrogen