foul

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Offensive to the senses; revolting.
• adjective Having a bad odor or taste.
• adjective Rotten or putrid.
• adjective Containing dirt, impurities, or other foreign matter;
• adjective Clogged or bestrewn with unwanted material.
• adjective Overgrown or encrusted with weeds, barnacles, or other organisms. Used of a ship's bottom.
• adjective Entangled or enwrapped.
• adjective Morally detestable; wicked.
• adjective Vulgar or obscene.
• adjective Violating accepted standards or rules; dishonorable.
• adjective Very disagreeable or displeasing; horrid.
• adjective Inclement or unfavorable.
• adjective Irritable or upset.
• adjective Sports Contrary to the rules of a game or sport.
• adjective Baseball Outside the foul lines.
• adjective Marked with editorial changes or corrections.
• adjective Archaic Ugly; unattractive.
• noun Sports An infraction or a violation of the rules of play.
• noun Baseball A foul ball.
• noun An entanglement or a collision.
• noun An instance of clogging or obstructing.
• noun A foul copy of a document.
• adverb In a foul manner.
• intransitive verb To make dirty or foul; pollute. synonym: contaminate.
• intransitive verb To bring into dishonor; besmirch.
• intransitive verb To clog or obstruct.
• intransitive verb To entangle or catch (a rope, for example).
• intransitive verb To encrust (a ship's hull) with foreign matter, such as barnacles.
• intransitive verb Sports To commit a foul against.
• intransitive verb Baseball To hit (a ball) outside the foul lines.
• intransitive verb To become foul.
• intransitive verb Sports To commit a foul.
• intransitive verb Baseball To hit a ball outside the foul lines.
• intransitive verb To become entangled or twisted.
• intransitive verb To become clogged or obstructed.

from The Century Dictionary.

• noun An obsolete spelling of fowl.
• To make foul, in any sense; befoul.
• Nautical, to entangle.
• To become foul or dirty: as, a gun. fouls from long use.
• Nautical, to come into collision, as two boats; become entangled or clogged: as, the rope fouled; the block fouled.