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1.
abbr. (phrase) fuck your shit up
often used in instant messaging following "I am going to..." when chatting with a person you dislike and would possibly punch and/or fight
Joey: Martin I am going to fysu you n00b
Martin: I will kill you Joe, bring it on
Joey: Any day biz-natch
by Joey Boone November 20, 2005
 
2.
FYSU means "fuck your shit up" it is used to define a reject dance crew who thinks they are "hardcore" and can fuck people up in "pits" at shows fitting the hardcore music genera usual FYSU members are wussies who go to shows looking to start a fight and cannot dance well at all
these kids are normally imposter's fakes and wanna be scene kids who don't know music at all

This term was first coined in 2010 in Panama city, Florida , US.

but is not limited to.

this term can be used to define any impostor "show scene dance crew"
just like DKC or DCM.

this can be used to define Pretty much a bunch of really gay assholes with no lives that go to shows and ruin it for every body also awful at the hxc 2 step
Steven"man i think am so hardcore and br00tal! im gonna fysu tonight!"
tanner" FYSU BRO FYSU!"
derek " FYSU is going to the show tonight!!were gonna fuck some kids up!!!"

*gets to show* steven: Hey see those kids over there having a good time? go behind them and kick them and start a brawl,and we will all jump the one person and try and look hardcore.

derek and his gang of posers join**

FYSU!
by ihatefysu March 23, 2010