The practice of wearing articles of clothing intended for the opposite sex. Attributed to Dr. Mangus Hirshchfeld, ca. 1919.

the practice of adopting the clothes or the manner or the sexual role of the opposite sex

There are many different usages and meanings of the term transvestism. Most experts agree that the correct usage is when people dress in clothes normally worn by the opposite gender in order to identify with that gender in some manner.

Dressing in clothes traditionally used by members of the opposite sex. In some people, cross-dressing may be a compulsion, or sexual arousal may be dependent upon cross-dressing. Many transvestites are heterosexual men whose behavior pattern does not lead to transsexualism (living and passing socially as a member of the opposite gender). Other transvestites are homosexual men ("drag queens"), who often develop elaborate feminine personas.