a day when, according to an old US custom, women can ask men to go out with them to start a romantic relationship, or women can ask men to dance with them at an event called a Sadie Hawkins dance. Sadie Hawkins Day is usually in November, and it is based on an imaginary character who first appeared in the US cartoon strip (=a set of drawings that tell a funny story in a newspaper or magazine) L'il Abner in the 1930s.
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.
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