Offensive to the senses; revolting:"a foul little creature with greedy eyes and slobbering mouth"(J.R.R. Tolkien). Having a bad odor or taste: foul breath; food that tasted foul. Rotten or putrid: foul meat. Containing dirt, impurities, or other foreign matter; foul water. Clogged or bestrewn with unwanted material: The bay is foul with old sunken vessels. Overgrown or encrusted with weeds, barnacles, or other organisms. Used of a ship's bottom. Entangled or enwrapped: a foul anchor. Morally detestable; wicked: foul deeds. Vulgar or obscene: foul language. Violating accepted standards or rules; dishonorable: used foul means to gain power. Very disagreeable or displeasing; horrid: a foul movie. Inclement or unfavorable: in fair weather or foul. Irritable or upset: in a foul mood. Sports Contrary to the rules of a game or sport: a foul boxing punch. Baseball Outside the foul lines: a foul fly ball. Marked with editorial changes or corrections: foul copy. Archaic Ugly; unattractive. Abbr. Sports An infraction or a violation of the rules of play. Baseball A foul ball. An entanglement or a collision. An instance of clogging or obstructing. A foul copy of a document. To make dirty or foul; pollute. See Synonyms at contaminate. To bring into dishonor; besmirch. To clog or obstruct. To entangle or catch (a rope, for example). To encrust (a ship's hull) with foreign matter, such as barnacles. Sports To commit a foul against. Baseball To hit (a ball) outside the foul lines. To become foul. Sports To commit a foul. Baseball To hit a ball outside the foul lines: fouled twice and then struck out; fouled out to the catcher. To become entangled or twisted: The anchor line fouled on a rock. To become clogged or obstructed.