The Collaborative International Dictionary of English v.0.48:

Mugging \Mug"ging\, n. [p. pr. & vb. n. from mug, v.]
   A robbery; a taking of property by threatening (or
   performing) violence on the person who is robbed. See mug,
   v.

   Syn: robbery, holdup, stickup
        [PJC + WordNet 1.5]

WordNet (r) 3.0 (2006):

mugging
    n 1: assault with intent to rob