The Collaborative International Dictionary of English v.0.48:

Galley \Gal"ley\, n.; pl. Galleys. [OE. gale, galeie (cf. OF.
   galie, gal['e]e, LL. galea, LGr. ?; of unknown origin.]
   1. (Naut.) A vessel propelled by oars, whether having masts
      and sails or not; as:
      (a) A large vessel for war and national purposes; --
          common in the Middle Ages, and down to the 17th
          century.
      (b) A name given by analogy to the Greek, Roman, and other
          ancient vessels propelled by oars.
      (c) A light, open boat used on the Thames by customhouse
          officers, press gangs, and also for pleasure.
      (d) One of the small boats carried by a man-of-war.
          [1913 Webster]

   Note: The typical galley of the Mediterranean was from one
         hundred to two hundred feet long, often having twenty
         oars on each side. It had two or three masts rigged
         with lateen sails, carried guns at prow and stern, and
         a complement of one thousand to twelve hundred men, and
         was very efficient in mediaeval warfare. Galleons,
         galliots, galleasses, half galleys, and quarter galleys
         were all modifications of this type.
         [1913 Webster]

   2. The cookroom or kitchen and cooking apparatus of a vessel;
      -- sometimes on merchant vessels called the caboose.
      [1913 Webster]

   3. (Chem.) An oblong oven or muffle with a battery of
      retorts; a gallery furnace.
      [1913 Webster]

   4. [F. gal['e]e; the same word as E. galley a vessel.]
      (Print.)
      (a) An oblong tray of wood or brass, with upright sides,
          for holding type which has been set, or is to be made
          up, etc.
      (b) A proof sheet taken from type while on a galley; a
          galley proof.
          [1913 Webster]

   Galley slave, a person condemned, often as a punishment for
      crime, to work at the oar on board a galley. "To toil like
      a galley slave." --Macaulay.

   Galley slice (Print.), a sliding false bottom to a large
      galley. --Knight.
      [1913 Webster]

WordNet (r) 3.0 (2006):

galley slave
    n 1: a slave condemned to row in a galley
    2: a laborer who is obliged to do menial work [syn: drudge,
       peon, navvy, galley slave]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "galley slave":
   bargee, bargeman, barger, beast of burden, boat-handler, boater,
   boatman, boatsman, bondmaid, bondman, bondslave, bondsman,
   bondswoman, captive, chattel, chattel slave, churl, concubine,
   debt slave, dray horse, drudge, fag, ferrier, ferryman, gondolier,
   greasy grind, grind, grub, hack, helot, homager, liege, liege man,
   liege subject, lighterman, oar, oarsman, odalisque, peon, plodder,
   punter, rower, serf, servant, slave, slavey, slogger, subject,
   swot, theow, thrall, toiler, vassal, villein, waterman, workhorse,
   yachter, yachtsman