WordNet (r) 3.0 (2006):

undersexed
    adj 1: having a subnormal degree of sexual desire

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "undersexed":
   amorous, carnal, cold, erogenic, erogenous, erotic, erotogenic,
   fleshly, gamic, heterosexual, inhibited, libidinal, nuptial,
   oversexed, passionless, potent, procreative, sensual, sex, sexed,
   sexlike, sexual, sexy, straight, unresponsive, venereal,
   voluptuous