[1] : WordNet (r) 2.0

twosome
     n 1: two items of the same kind syn: couple, pair, twain,
          brace, span, yoke, couplet, distich, duo, duet,
           dyad, duad
     2: a pair who associate with one another; "the engaged couple";
        "an inseparable twosome" syn: couple, duo, duet
see also:
couple pair twain brace span yoke 
couplet distich duo duet dyad 
duad 

[2] : Moby Thesaurus II by Grady Ward, 1.0

40 moby thesaurus words for "twosome":
   both, bout, brace, contest, couple, couplet, decathlon, distich,
   double harness, double-header, doubles, doublet, duad, duet, duo,
   dyad, event, foursome, game, games of chance, go, match, mates,
   meet, pair, pentathlon, play, play-off, race, runoff, set of two,
   singles, span, sport, team, the two, threesome, twain, two, yoke

Twosome >> T Words
Twosome, definition of term: Twosome
twosome_pag1.html