The Collaborative International Dictionary of English v.0.48:

Whaler \Whal"er\, n.
   A vessel or person employed in the whale fishery.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Whaler \Whal"er\, n.
   One who whales, or beats; a big, strong fellow; hence,
   anything of great or unusual size. [Colloq. U. S.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

whaler
    n 1: a seaman who works on a ship that hunts whales
    2: a ship engaged in whale fishing [syn: whaler, whaling
       ship]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "whaler":
   AB, Ancient Mariner, Argonaut, Dylan, Flying Dutchman, Neptune, OD,
   Poseidon, Varuna, able seaman, able-bodied seaman, angler,
   bluejacket, buccaneer, deep-sea man, dibber, dibbler, drift netter,
   drifter, fair-weather sailor, fisher, fisherman, guddler, hearty,
   jack, jack afloat, jack-tar, jacker, jacky, jigger, limey,
   lobsterman, mariner, matelot, navigator, pirate, piscator,
   piscatorialist, piscatorian, privateer, sailor, salt, sea dog,
   sea rover, seafarer, seafaring man, seaman, shipman, tar,
   the compleat angler, trawler, troller, viking, water dog,
   windjammer, windsailor



Bouvier's Law Dictionary, Revised 6th Ed (1856):

WHALER, mar. law. A vessel employed in the whale fishery.
     2. It is usual for the owner of the vessel, the captain and crew, to
divide the profits in just proportions, under an agreement similar to the
contract Di Colonna. (q.v.)