From WordNet (r) 3.0 (2006) [wn]:
fivesome
n 1: the cardinal number that is the sum of four and one [syn:
five, 5, V, cinque, quint, quintet, fivesome,
quintuplet, pentad, fin, Phoebe, Little Phoebe]
2: five people considered as a unit [syn: quintet,
quintette, fivesome]