The Collaborative International Dictionary of English v.0.48:

Wigwag \Wig"wag`\, v. i. [See Wag, v. t.] (Naut.)
   To signal by means of a flag waved from side to side
   according to a code adopted for the purpose. [Colloq.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wigwag \Wig"wag`\, v. t. & i. [imp. & p. p. Wigwagged; p. pr.
   & vb. n. Wigwagging.]
   To move to and fro, to wag.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Wigwag \Wig"wag`\, n. [See Wigwag, v. t. & i.]
   Act or art of wigwagging; a message wigwagged; -- chiefly
   attributive; as, the wigwag code. -- Wig"wag`er, n.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

wigwag
    v 1: send a signal by waving a flag or a light according to a
         certain code
    2: signal by or as if by a flag or light waved according to a
       code