1. Also called Sadie, Sa'dies. a party, dance, or other social event, esp. one held annually among high school or college students, to which each girl escorts the boy of her choice, or invites him to escort her.
2. a day (Sa'die Haw'kins Day") or night, often in November, when such an event or events are held.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.