The Collaborative International Dictionary of English v.0.48:

Castaway \Cast"a*way\, n.
   1. One who, or that which, is cast away or shipwrecked.
      [1913 Webster]

   2. One who is ruined; one who has made moral shipwreck; a
      reprobate.
      [1913 Webster]

            Lest . . . when I have preached to others, I myself
            should be a castaway.                 --1 Cor. ix.
                                                  27.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Castaway \Cast"a*way\, a.
   Of no value; rejected; useless.
   [1913 Webster]

WordNet (r) 3.0 (2006):

castaway
    n 1: a person who is rejected (from society or home) [syn:
         outcast, castaway, pariah, Ishmael]
    2: a shipwrecked person [syn: castaway, shipwreck survivor]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "castaway":
   DP, Ishmael, abandoned, aground, cast-off, castoff, declasse,
   deep six, derelict, deserted, discard, discarded, discarding,
   disowned, displaced person, disposal, disused, dogie, dumping,
   elimination, evictee, exile, expatriate, expellee, flotsam,
   flotsam and jetsam, forsaken, foundered, foundling, grounded,
   high and dry, jetsam, jettison, jettisoned, junk, junking, lagan,
   left, leper, marooned, on the rocks, orphan, outcast,
   outcast of society, outcaste, outlaw, outside the gates,
   outside the pale, pariah, persona non grata, refuse, reject,
   rejectamenta, rejected, rejection, removal, rubbish, scrapping,
   set fast, shipwrecked, social outcast, stranded, stuck, stuck fast,
   swamped, throwaway, trash, unacceptable person, undesirable,
   untouchable, waif, waifs and strays, wastrel, wrecked



Easton's 1897 Bible Dictionary:

Castaway
   Gr. adokimos, (1 Cor. 9:27), one regarded as unworthy (R.V.,
   "rejected"); elsewhere rendered "reprobate" (2 Tim. 3:8, etc.);
   "rejected" (Heb. 6:8, etc.).