Source : Webster's Revised Unabridged Dictionary (1913)

Humorless \Hu"mor*less\, a.
   Destitute of humor.

Source : WordNet®

humorless
     adj : lacking humor; "it was a humorless wink; a wink of warning"-
           Truman Capote [syn: {humourless}, {unhumorous}] [ant: {humorous}]