foul

Concise Oxford English Dictionary © 2008 Oxford University Press:
foul/faʊl/

▶adjective

• 1 offensive to the senses.

  ■ informal very disagreeable or unpleasant.

  ■ (of the weather) wet and stormy.

• 2 morally offensive; wicked or obscene.

  ■ done contrary to the rules of a sport.

• 3 polluted or contaminated.

  ■ (foul with) clogged or choked with.

  ■ Nautical (of a rope or anchor) entangled.

▶noun (in sport) an unfair or invalid stroke or piece of play.

■ a collision or entanglement in riding, rowing, or running.

▶verb

• 1 make foul; pollute.

  ■ make dirty with excrement.

• 2 (in sport) commit a foul against.

• 3 (foul something up or foul up) make a mistake with or spoil something.

• 4 (of a ship) collide with or interfere with the passage of (another).

  ■ cause (a cable, anchor, etc.) to become entangled or jammed.

– derivatives
foully adverb,
foulness noun.

– origin OE fūl, of Gmc origin.