when you start swearing and saying all this crap to someone
That guy Marc was really starting to tick me off, so i started mouthing off
by Kayla May 8, 2004
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that bitch has a reputation four mouthing off at the worst possible moments, I should cut her throat before she says any other stuff!

don't mouth off at me, you fuckin prick
by biancavittoria February 10, 2014
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When two hardcore metalhead slayer fans argue, possibly for hours, about how much they know about slayer ect. it is a diverse bonding ritual of slayer fans, when they feel threatened by another slayer fan. slayer fans don't usually like other slayer fans.
typical slayer mouth-off..

slayer fan #1: how many slayer tee shirts do you have?
slayer fan #2: 5. how many do you have?
slayer fan #1: 5. how many slayer albums do you have?
slayer fan #2: all of them. how many do you have?
slayer fan #1: all of them including the one that they never actually released. i had to drug Tom Araya to get it..
slayer fan #2: well i have the limited edition slayer action figures!!!
slayer fan #1: how come i'v never seen them in your room?
slayer fan #2: because i hide them under my bed!
slayer fan #1: fuck you man, you just dissed slayer i'm gunna have to kill you.
slayer fan #2: *brutally mutilated* lets put on some slayer.
by Your Cats On Fire! January 3, 2010
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When all someone does is talk shit and the more they do the more toxic waste comes out.
Guy: I can't stand John Walsh. All he does is talk about fugitives being on the loose! He needs to get a life!

Girl: Quit jerking your mouth off. I can smell the shit when you open it.
by Luna Belle December 11, 2009
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