Extremely unpleasant to the senses or feelings
Having an unpleasant odor
Heavily soiled; very dirty or unclean
Offensive to accepted standards of decency
So objectionable as to elicit despisal or deserve condemnation
To make physically impure
To twist together so that separation is difficult
To harm irreparably through inept handling; make a mess
Obscene or abusive
To make dirty
To become dirty or entangled
run or fall foul of
The foul smelling grease turned her stomach.
Rumour attributed his death to foul play.
I read all the weekly newspapers and there was no mention of any foul play, but this little ad caught my attention.
The foul air, to which he had already begun to get used in the corridor, was still stronger here.
"If it doesn't work, no harm, no foul," she said.