Source : Webster's Revised Unabridged Dictionary (1913)

Shrug \Shrug\, v. t. [imp. & p. p. {Shrugged}; p. pr. & vb. n.
   {Shrugging}.] [Probably akin to shrink, p. p. shrunk; cf.
   Dan. skrugge, skrukke, to stoop, dial. Sw. skrukka, skruga,
   to crouch.]
   To draw up or contract (the shoulders), especially by way of
   expressing dislike, dread, doubt, or the like.

         He shrugs his shoulders when you talk of securities.
                                                  --Addison.

Shrug \Shrug\, v. i.
   To raise or draw up the shoulders, as in expressing dislike,
   dread, doubt, or the like.

         They grin, they shrug. They bow, they snarl, they
         snatch, they hug.                        --Swift.

Shrug \Shrug\, n.
   A drawing up of the shoulders, -- a motion usually expressing
   dislike, dread, or doubt.

         The Spaniards talk in dialogues Of heads and shoulders,
         nods and shrugs.                         --Hudibras.

Source : WordNet®

shrug
     n : a gesture involving the shoulders
     [also: {shrugging}, {shrugged}]

shrug
     v : raise one's shoulders to indicate indifference or
         resignation
     [also: {shrugging}, {shrugged}]