WordNet (r) 3.0 (2006):

sex drive
    n 1: a physiological need for sexual activity; "testosterone is
         responsible for the male sex drive"

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "sex drive":
   carnality, coldness, flesh, fleshliness, frigidity, impotence,
   libido, love, lovemaking, marriage, potency, sensuality, sexiness,
   sexual instinct, sexual urge, sexualism, sexuality,
   voluptuousness