The Collaborative International Dictionary of English v.0.48:

Roustabout \Roust"a*bout`\, n. [Etymol. uncertain.]
   A laborer, especially a deck hand, on a river steamboat, who
   moves the cargo, loads and unloads wood, and the like; in an
   opprobrious sense, a shiftless vagrant who lives by chance
   jobs. [Western U.S.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

roustabout
    n 1: a member of a ship's crew who performs manual labor [syn:
         deckhand, roustabout]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "roustabout":
   bakehead, black gang, blue-collar worker, boilerman, breadwinner,
   bungs, cabin boy, casual, casual laborer, chips,
   commissary steward, common laborer, complement, day laborer,
   deckhand, deckie, docker, dockhand, employee, factory worker,
   fireman, flunky, free lance, free-lancer, full-time worker,
   gun loader, gunner, hand, hospital steward, industrial worker,
   jobber, jobholder, laborer, laboring man, landing signalman,
   loader, longshoreman, mail orderly, menial, migrant, moiler,
   navigator, navvy, office temporary, oiler, operative, proletarian,
   purser, radio operator, salaried worker, self-employed person,
   servant, snip, snips, sparks, stevedore, steward, stewardess,
   stiff, stoker, temporary, toiler, torpedoman, wage earner,
   wage slave, wageworker, watch, wharf hand, worker, workgirl,
   workhand, working girl, workingman, workingwoman, workman,
   yeoman