The Collaborative International Dictionary of English v.0.48:

Horny \Horn"y\, a. [Compar. Hornier; superl. Horniest.]
   1. Having horns or hornlike projections. --Gay.
      [1913 Webster]

   2. Composed or made of horn, or of a substance resembling
      horn; of the nature of horn. "The horny . . . coat of the
      eye." --Ray.
      [1913 Webster]

   3. Hard; callous. "His horny fist." --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

horny
    adj 1: feeling great sexual desire; "feeling horny" [syn:
           aroused, horny, randy, ruttish, steamy, turned
           on(p)]
    2: having horns or hornlike projections; "horny coral"; "horny
       (or horned) frog"
    3: made of horn (or of a substance resembling horn) [syn:
       corneous, hornlike, horny]