Table of Contents POS
HYPHEN
WORDNET DICTIONARY
OXFORD DICTIONARY
THESAURUS

WORDNET DICTIONARY

Noun threesome has 2 senses

• threesome(n = noun.quantity) 3, deuce-ace, iii, leash, tercet, ternary, ternion, terzetto, three, tierce, trey, triad, trine, trinity, trio, triplet, troika - the cardinal number that is the sum of one and one and one; Array
is a kind of digit, figure

• threesome(n = noun.group) triad, trinity, trio - three people considered as a unit; Array
is a kind of assemblage, gathering
has particulars: triumvirate

OXFORD DICTIONARY

THESAURUS

threesome

bout, clover, contest, decathlon, deuce-ace, double-header, doubles, event, foursome, game, games of chance, go, leash, match, meet, pentathlon, play, play-off, race, runoff, set of three, shamrock, singles, sport, tercet, ternary, ternion, terzetto, three, tierce, trefoil, trey, triad, trialogue, triangle, tricorn, trident, triennium, trihedron, trilogy, trimester, trine, trinity, trinomial, trio, triphthong, triple, triple crown, triple threat, triplet, triplopy, tripod, triptych, trireme, triseme, triskelion, trisul, triumvirate, triune, triunity, trivet, troika, twosome

For further exploring for "threesome" in Webster Dictionary Online