n. 25B6; adjective
a foul stench : DISGUSTING, revolting, repulsive, repugnant, abhorrent, loathsome, offensive, sickening, nauseating, nauseous, stomach-churning, stomach-turning, distasteful, obnoxious, objectionable, odious, noxious; N. Amer. vomitous; informal ghastly, gruesome, gross, putrid, yucky, skanky, sick-making; Brit. informal beastly; Austral. informal on the nose; poetic/literary miasmic, noisome, mephitic.
a foul mess : DIRTY, filthy, mucky, grimy, grubby, muddy, muddied, unclean, unwashed; squalid, sordid, soiled, sullied, scummy; rotten, defiled, decaying, putrid, putrefied, smelly, fetid; informal cruddy, yucky, icky; Brit. informal manky, gungy, grotty; rare feculent.
he had been foul to her : UNKIND, malicious, mean, nasty, unpleasant, unfriendly, spiteful, cruel, vicious, base, malevolent, despicable, contemptible; informal horrible, horrid, rotten; Brit. informal beastly.
foul weather : INCLEMENT, unpleasant, disagreeable, bad; rough, stormy, squally, gusty, windy, blustery, wild, blowy, rainy, wet; Brit. informal filthy.
foul drinking water : CONTAMINATED, polluted, infected, tainted, impure, filthy, dirty, unclean; rare feculent.
a foul deed : EVIL, wicked, bad, wrong, immoral, sinful, vile, dishonourable, corrupt, iniquitous, depraved, villainous, nefarious, vicious, malicious; malevolent, sinister, demonic, devilish, diabolical, fiendish, dark; monstrous, shocking, despicable, atrocious, heinous, odious, contemptible, horrible, execrable; informal low-down, dirty.
foul language : VULGAR, crude, coarse, filthy, dirty, obscene, indecent, indelicate, naughty, lewd, suggestive, smutty, ribald, salacious, scatological, offensive, abusive; informal blue.
a foul tackle : UNFAIR, illegal, unsporting, unsportsmanlike, below the belt, dirty.
pleasant, kind, fair, clean, righteous, mild, fair.
25B6; verb
the river had been fouled with waste : DIRTY, infect, pollute, contaminate, poison, taint, sully, soil, stain, blacken, muddy, splash, spatter, smear, blight, defile, make filthy.
the vessel had fouled her nets : TANGLE UP, entangle, snarl, catch, entwine, enmesh, twist.
clean up, disentangle.