The Collaborative International Dictionary of English v.0.48:

Mariner \Mar"i*ner\, n. [F. marinier, LL. marinarius. See
   Marine.]
   One whose occupation is to assist in navigating ships; a
   seaman or sailor. --Chaucer.
   [1913 Webster]

   Mariner's compass. See under Compass.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mariner
    n 1: a man who serves as a sailor [syn: mariner, seaman,
         tar, Jack-tar, Jack, old salt, seafarer, gob,
         sea dog]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "mariner":
   adventurer, alpinist, astronaut, bluejacket, camper, climber,
   comers and goers, commuter, cosmopolite, cruiser, excursionist,
   explorer, fare, globe-girdler, globe-trotter, gob, goer, hajji,
   jack, jack-tar, jet set, jet-setter, journeyer, limey, mountaineer,
   old salt, palmer, passenger, passerby, pathfinder, pilgrim,
   pioneer, rating, rubberneck, rubbernecker, sailor, salt, sea dog,
   seaman, shellback, sightseer, straphanger, swab, swabbie, tar,
   tarpaulin, tourer, tourist, trailblazer, trailbreaker, transient,
   traveler, trekker, tripper, viator, visiting fireman, voortrekker,
   voyager, voyageur, wayfarer, world-traveler



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

MARINER. One whose occupation is to navigate vessels on the sea. Vide Seamen
Shipping articles.
     2. By act of congress, 1 Story, Laws of U. S., ch. 56, s. 4, p. 109, it
is provided, that no sum exceeding one dollar shall be recovered from any
seaman or mariner (in the merchant service,) by any person, for any debt
contracted during the time such seaman or mariner shall actually belong to
any ship or vessel, until the voyage for which such seaman or mariner
engaged, shall be ended.