Source : Webster's Revised Unabridged Dictionary (1913)

Whack \Whack\, v. t. [imp. & p. p. {Whacked}; p. pr. & vb. n.
   {Whacking}.] [Cf. {Thwack}.]
   To strike; to beat; to give a heavy or resounding blow to; to
   thrash; to make with whacks. [Colloq.]

         Rodsmen were whackingtheir way through willow brakes.
                                                  --G. W. Cable.

Source : WordNet®

whacked
     adj : (British informal) exhausted or worn out