The faux illness your girlfriend/boyfriend gets on a weekend night preventing you from going to meet up with your friends as originally planned.
Dude 1: Didn't Mess say he was coming tonight?
Dude 2: Naw, his girlfriend caught the Friday Night Flu.
by HairySally February 1, 2008
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When you spouse gets sick on Friday so you have to watch the kids all weekend. Usually last two days.
I hope my wife doesn't get Friday Flu again, I want to play golf.
by Herod apyur pupir February 24, 2017
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