Source : Webster's Revised Unabridged Dictionary (1913)

Billy \Bil"ly\, n.
   1. A club; esp., a policeman's club.

   2. (Wool Manuf.) A slubbing or roving machine.

Source : WordNet®

billy
     n 1: a short stout club used primarily by policemen [syn: {truncheon},
           {nightstick}, {billystick}, {billy club}]
     2: male goat [syn: {billy goat}, {he-goat}]