The Collaborative International Dictionary of English v.0.48:

Martin \Mar"tin\, n. [F. martin, from the proper name Martin.
   Cf. Martlet.] (Zool.)
   One of several species of swallows, usually having the tail
   less deeply forked than the tail of the common swallows.
   [Written also marten.]
   [1913 Webster]

   Note: The American purple martin, or bee martin (Progne
         subis or Progne purpurea), and the European house
         martin, or window martin (Hirundo urbica or
         Chelidon urbica), are the best known species.
         [1913 Webster]

   Bank martin.
   (a) The bank swallow. See under Bank.
   (b) The fairy martin. See under Fairy.

   Bee martin.
   (a) The purple martin.
   (b) The kingbird.

   Sand martin, the bank swallow.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bank martin
    n 1: swallow of the northern hemisphere that nests in tunnels
         dug in clay or sand banks [syn: bank martin, bank
         swallow, sand martin, Riparia riparia]