[prob. an attributive or elliptic use of prec.] (See quots.)

1

1849.  D. J. Browne, Amer. Poultry Yd. (1855), 290. In 1823, he [a game-cock] was milk-white, or ‘smock,’ as the English term it.

2

1854.  Meall, Moubray’s Poultry, 111. [Sub-varieties of Game-Fowl.] White, or Smock (vulgar).

3