Source : Webster's Revised Unabridged Dictionary (1913)

Foul \Foul\, n.
   In various games or sports, an act done contrary to the
   rules; a foul stroke, hit, play, or the like.

Foul \Foul\ (foul), n. [See {Fowl}.]
   A bird. [Obs.] --Chaucer.

Foul \Foul\ (foul), a. [Compar. Fouler (-[~e]r); superl.
   {Foulest}.] [OE. foul, ful, AS. f[=u]l; akin to D. vuil, G.
   faul rotten, OHG. f[=u]l, Icel. f[=u]l foul, fetid; Dan.
   fuul, Sw. ful foul, Goth. f[=u]ls fetid, Lith. puti to be
   putrid, L. putere to stink, be putrid, pus pus, Gr. py`on
   pus, to cause to rot, Skr. p[=u]y to stink. [root]82. Cf.
   {Defile} to foul, {File} to foul, {Filth}, {Pus}, {Putrid}.]
   1. Covered with, or containing, extraneous matter which is
      injurious, noxious, offensive, or obstructive; filthy;
      dirty; not clean; polluted; nasty; defiled; as, a foul
      cloth; foul hands; a foul chimney; foul air; a ship's
      bottom is foul when overgrown with barnacles; a gun
      becomes foul from repeated firing; a well is foul with
      polluted water.

            My face is foul with weeping.         --Job. xvi.
                                                  16.

   2. Scurrilous; obscene or profane; abusive; as, foul words;
      foul language.

   3. Hateful; detestable; shameful; odious; wretched. ``The
      foul with Sycorax.'' --Shak.

            Who first seduced them to that foul revolt?
                                                  --Milton.

   4. Loathsome; disgusting; as, a foul disease.

   5. Ugly; homely; poor. [Obs.] --Chaucer.

            Let us, like merchants, show our foulest wares.
                                                  --Shak.

   6. Not favorable; unpropitious; not fair or advantageous; as,
      a foul wind; a foul road; cloudy or rainy; stormy; not
      fair; -- said of the weather, sky, etc.

            So foul a sky clears not without a storm. --Shak.

   7. Not conformed to the established rules and customs of a
      game, conflict, test, etc.; unfair; dishonest;
      dishonorable; cheating; as, foul play.

   8. Having freedom of motion interfered with by collision or
      entanglement; entangled; -- opposed to clear; as, a rope
      or cable may get foul while paying it out.

Foul \Foul\, v. i.
   1. To become clogged with burnt powder in the process of
      firing, as a gun.

   2. To become entagled, as ropes; to come into collision with
      something; as, the two boats fouled.

Foul \Foul\, n.
   1. An entanglement; a collision, as in a boat race.

   2. (Baseball) See {Foul ball}, under {Foul}, a.

Foul \Foul\, v. t. [imp. & p. p. {Fouled}; p. pr. & vb. n.
   {Fouling}.]
   1. To make filthy; to defile; to daub; to dirty; to soil; as,
      to foul the face or hands with mire.

   2. (Mil.) To incrust (the bore of a gun) with burnt powder in
      the process of firing.

   3. To cover (a ship's bottom) with anything that impered its
      sailing; as, a bottom fouled with barnacles.

   4. To entangle, so as to impede motion; as, to foul a rope or
      cable in paying it out; to come into collision with; as,
      one boat fouled the other in a race.

Source : WordNet®

foul
     adj 1: highly offensive; arousing aversion or disgust; "a
            disgusting smell"; "distasteful language"; "a
            loathsome disease"; "the idea of eating meat is
            repellent to me"; "revolting food"; "a wicked stench"
            [syn: {disgusting}, {disgustful}, {distasteful}, {loathly},
             {loathsome}, {repellent}, {repellant}, {repelling}, {revolting},
             {skanky}, {wicked}, {yucky}]
     2: offensively malodorous; "a putrid smell" [syn: {fetid}, {foetid},
         {foul-smelling}, {funky}, {noisome}, {smelly}, {putrid},
        {stinking}]
     3: violating accepted standards or rules; "a dirty fighter";
        "used foul means to gain power"; "a nasty unsporting
        serve"; "fined for unsportsmanlike behavior" [syn: {cheating(a)},
         {dirty}, {unsporting}, {unsportsmanlike}]
     4: (of a baseball) not hit between the foul lines [ant: {fair}]
     5: (of a manuscript) defaced with changes; "foul (or dirty)
        copy" [syn: {dirty}, {marked-up}]
     6: thoroughly unpleasant; "filthy (or foul or nasty or vile)
        weather we're having" [syn: {filthy}, {nasty}, {vile}]
     7: characterized by obscenity; "had a filthy mouth"; "foul
        language"; "smutty jokes" [syn: {filthy}, {nasty}, {smutty}]
     8: disgustingly dirty; filled or smeared with offensive matter;
        "as filthy as a pigsty"; "a foul pond"; "a nasty pigsty of
        a room" [syn: {filthy}, {nasty}]
     9: especially of a ship's lines etc; "with its sails afoul"; "a
        foul anchor" [syn: {afoul(ip)}, {fouled}]

foul
     n : an act that violates of the rules of a sport

foul
     v 1: hit a foul ball
     2: make impure; "The industrial wastes polluted the lake" [syn:
         {pollute}, {contaminate}]
     3: become or cause to become obstructed; "The leaves clog our
        drains in the Fall"; "The water pipe is backed up" [syn: {clog},
         {choke off}, {clog up}, {back up}, {congest}, {choke}]
        [ant: {unclog}]
     4: commit a foul; break the rules
     5: spot, stain, or pollute; "The townspeople defiled the river
        by emptying raw sewage into it" [syn: {befoul}, {defile},
        {maculate}]
     6: make unclean; "foul the water"
     7: become soiled and dirty