Synonyms for foul

modified

1. Soiled

   dirty, unclean, filthy, impure; see dirty 1.

2. Disgusting

   loathsome, fetid, odious; see offensive 2, rank 2.

3. Obscene or abusive

   nasty, vulgar, coarse; see lewd 1, opprobrious 1, ribald.

4. Unfair

   inequitable, unjust, dishonorable, vicious; see dishonest 2.

run<strong> or </strong>fall foul of

verb

1. To make dirty

   defile, pollute, sully, soil; see dirty.

2. To become dirty or entangled

   soil, spot, discolor, stain, clog, jam, snarl, catch, be clogged, be choked, be tangled, be coated, be encrusted, be blocked, be filled.