Source : Webster's Revised Unabridged Dictionary (1913)

Highwayman \High"way`man\, n.; pl. {Highwaymen}.
   One who robs on the public road; a highway robber.

Source : WordNet®

highwayman
     n : a holdup man who stops a vehicle and steals from it [syn: {highjacker},
          {hijacker}, {road agent}]