The Collaborative International Dictionary of English v.0.48:

Gam \Gam\ (g[a^]m), n. [fr. gamba leg.]
   a leg. [slang]
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Gam \Gam\ (g[a^]m), v. i. [imp. & p. p. Gammed; p. pr. & vb.
   n. Gam"ming.] (Naut.)
   (a) To gather in a gam; -- said of whales.
   (b) To engage in a gam, or (Local, U. S.) in social
       intercourse anywhere.
       [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Gam \Gam\ (g[a^]m), v. t. (Naut.)
   To have a gam with; to pay a visit to, esp. among whalers at
   sea.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Gam \Gam\ (g[a^]m), n. [Orig. uncert., perh. from gammon, talk.]
   1. (Naut.) A herd, or school, of whales.
      [Webster 1913 Suppl.]

   2. A visit between whalers at sea; a holding of social
      intercourse between those on different vessels at sea, or
      (Local U. S.) between persons ashore.
      [Webster 1913 Suppl.]

   3. A visit between whalers at sea; a holding of social
      intercourse between those on different vessels at sea, or
      (Local U. S.) between persons ashore.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

gam
    n 1: a herd of whales