Other forms: fouled, fouls, fouling
In sport, a foul is a move against the rules that the referee stops at once. Commit a foul, a professional foul, fouled in the box.
The older, wider meaning is disgusting or offensive: a foul smell, foul weather, foul language. Both are entirely current, and the sporting sense grew out of the other. Note foul play, which in a police report means violence rather than a rule breach, and fall foul of, meaning to get into trouble with a rule or a person. And the homophone fowl means a bird, which is a distinction worth having before writing about chickens.
1nounfoulAn action against the rules in a sport.
“It was a clear foul and everybody in the ground saw it.”
2adjectivedisgustingVery unpleasant, especially in smell or taste.
“There was a foul smell coming from the drain.”
synonyms: disgusting, revolting, rank
3adjectiveweatherOf weather, very bad.
“They set off in foul weather and regretted it.”
4verbcommitTo commit a foul against a player.
“He was fouled just outside the area.”
Too few real examples of this word to estimate which sense is commonest.
foul is a rule breach, or a quality of unpleasantness.
Old English ful meant rotten or stinking, from a Proto-Indo-European root meaning to rot — the same root as putrid and pus. Every modern sense comes from that smell: dirty, then offensive, then against the rules.
Proto-Indo-European
*puH- — foul, rotten
Proto-Germanic
*fūlaz — foul, rotten
Proto-West Germanic
*fūl
Old English
fūl — foul, dirty, unclean, impure, vile, corrupt, rotten, stinking, guilty
Middle English
ffoul
English, today
foul
Middle English ffoul, foul, foull, fowel, fowle, fuyle, voul, vul, from Old English fūl (“foul, dirty, unclean, impure, vile, corrupt, rotten, stinking, guilty”), from Proto-West Germanic fūl, from Proto-Germanic fūlaz (“foul, rotten”), from Proto-Indo-European puH- (“foul, rotten”). 2 Cognate with gmw-cfr fuul (“putrid, rotten; lazy, workshy”), cim baul, vaul (“putrid, rotten”), Dutch vuil (“dirty, foul; lewd, obscene; dishonorable; illegal”), German faul (“foul, putrid, rotten; lazy”), Yiddish פֿױל (“putrid; lazy”), Danish ful (“nasty, ugly”), Icelandic fúll (“foul, rotten, sullen”), Norwegian Bokmål and Norwegian Nynorsk ful (“clever, sly”), and Swedish ful (“ugly; bad, dirty”), Gothic 𐍆𐌿𐌻𐍃 (“fetid, foul, putrid”), and through Indo-European, with Latin puter (“decaying, rotten; friable, crumbling”), Greek πύο, πύον (“pus”), Albanian fëlliq (“to make dirty, sully”), Latvian pūt (“to rot”), Lithuanian pūti (“to rot”), Armenian փուտ (“rottenness”), Persian پوده (“rubbed, worn; foul, rotten; empty, hollow”), Sanskrit पूयति (“to become foul; to stink”). More at putrid.
Etymology from Wiktionary, CC BY-SA