The day where cussing, cursing, or swearing is used to gain points. A game to find who can use the most cuss words in one day. The use of f'k and other variations of such are used frequently. A generous amount of points are rewarded when one has used vowels.
Made popular by the Twilight Saga fanfiction, If Every Word I Said Could Make You Laugh (IEWIS), and continued in use in the sequel, More More More (MMM) both written by carmelinagunn (username on fanfiction.net).
"Seriously? You're proposing that we reinstate Cussin' Day?" I asked with a small laugh as I poured some lemonade into the glass I took out.
They both started laughing and Rose said, "Eh, we're pretty sure the boys made today an official Cussin' Day and we're pretty amused by it."
-Both Excerpts from MMM