The day on which you fap. May also be spelled Fapjous Day.

A play on Fraptious Day from the new Alice in Wonderland.
Carmin would wait until Sunday, which is after Saturday -- the day on which she always attempts to get laid, to masturbate. That way, she would be ready should the chance to have sex arise before then. Thus Carmin dubbed Sunday her Faptious Day.
by The Blanket Monster May 7, 2011
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