Source : Webster's Revised Unabridged Dictionary (1913)

Martlet \Mart"let\, n. [F. martinet. See {Martin} the bird, and
   cf. {Martinet} a disciplinarian.]
   1. (Zo["o]l.) The European house martin.

   2. [Cf. F. merlette.] (Her.) A bird without beak or feet; --
      generally assumed to represent a martin. As a mark of
      cadency it denotes the fourth son.