Lascivious
From Academic Kids
In general use, lascivious is synonymous with lustful.
In American legal jargon, lascivious is a semi-technical term indicating immoral sexual thoughts or actions. It is often used in the legal description of criminal acts in which some sort of sexual activity is prohibited to differentiate that activity from innocent conduct.
For example, a lewd or lascivious act would refer to sex crimes such as child rape. Whether an action amounts to lascivious conduct rests to a large degree on whether society is currently condemning the action. For example, lascivious cohabitation refers to a mostly archaic crime of living with a member of the opposite sex, and having sexual intercourse with him or her.
See e.g. Swearingen v. U.S., 161 U.S. 446
Similar legal topics include obscene.
