Noun
jailbait (usually uncountable, plural jailbaits)
(slang) A sexually mature person below, or appearing to be below, the legal age of consent, who is regarded, usually by an adult, as being "temptingly" attractive and/or seductive.
Ummm...” She licked her lips. "Define fun.” "Quit doing that, jailbait. It's distracting. Rachel Caine