The Collaborative International Dictionary of English v.0.48:

big-shouldered \big-shouldered\ adj.
   having unusually large shoulders. big-shouldered and
   heavy-armed

   Syn: broad-shouldered, square-shouldered.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

big-shouldered
    adj 1: having broad shoulders; "big-shouldered and heavy-armed"
           [syn: big-shouldered, broad-shouldered, square-
           shouldered]