The Collaborative International Dictionary of English v.0.48:

vamoose \va*moose"\ (v[a^]*m[=oo]s"), v. i. & t. [Sp. vamos let
   us go.]
   To depart quickly; to depart from. [Written also vamos, and
   vamose.] [Slang, Eng. & U. S.]
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

vamose \va*mose"\ (v[.a]*m[=o]s"), v. i. & t. [Sp. vamos let us
   go.]
   To vamoose; -- an older spelling and pronunciation variant.
   [Written also vamos, and vamoose.] [Slang, Eng. & U. S.]
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

vamoose
    v 1: leave suddenly; "She persuaded him to decamp"; "skip town"
         [syn: decamp, skip, vamoose]