What is Foul?
1.
Really shitty.
Fucked up.
Rotten, spoiled.
Not right, psychologically.
Stolen.
Man, that blowjob was foul, she bit my dick!
That motherfucker was one foul biatch.
I'm not buying that shit, it's foul!
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2.
The filthiest of the filthy. Foul refers to the smell of a filthy bitch /
Shut your legs, you're making this room smell foul you slut!
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3.
Impure or not within the confines of acceptable normalcy.
"Man I know Turkeys and Chickens stink, but that fowl farm is fucking foul."
"Dude, you hit a baseball like you smell, and that would be foul"
4.
'Foul' can also be used as a positive adjective.
e.g.'Those trainers are totally foul, dude', meaning 'Those trainers are really rather cool'.