trans·ves·tism 
(trăns-vĕstĭz′əm, trănz-) also trans·ves·ti·tism (-tĭ-tĭz′əm)
(trăns-vĕstĭz′əm, trănz-) also trans·ves·ti·tism (-tĭ-tĭz′əm)n.
1. Psychiatry The deriving of sexual gratification from fantasies or acts that involve dressing in clothes traditionally associated with the opposite sex.
2. Cross-dressing. In this sense, the term is sometimes considered offensive.