Valentine n. : A sweetheart chosen on St. Valentine's Day.

Valentine n. : A letter containing professions of love, or a missive of a sentimental, comic, or burlesque character, sent on St. Valentine's Day.

Example:
What is the most romantic Valentine's Date you either planned or were taken on?

Taxonomy
Valentine, Valentine's Day, chocolate, Saint Valentine, February 14, holiday, St. Valentine, lovers, flowers, card, Valentine cards, Rome, tradition, observances, Terni, the Saints, choko, Saint Valentine's Day.

Defination from the web:
Valentine's Day, including its history and its equivalents in other cultures.