Source : Webster's Revised Unabridged Dictionary (1913)

Asinine \As"i*nine\, a. [L. asininus, fr. asinus ass. See
   {Ass}.]
   Of or belonging to, or having the qualities of, the ass, as
   stupidity and obstinacy. ``Asinine nature.'' --B. Jonson.
   ``Asinine feast.'' --Milton.

Source : WordNet®

asinine
     adj : complacently or inanely foolish [syn: {fatuous}, {inane}, {mindless},
            {vacuous}]