1. [n]  a wrong action attributable to bad judgment or ignorance or inattention; "he made a bad mistake"; "she was quick to point out my errors"; "I could understand his English in spite of his grammatical faults"
2. [n]  (tennis or badminton or squash) a serve that is illegal (e.g., that lands outside the prescribed area); "he served too many double faults"
3. [n]  responsibility for a bad situation or event; "it was John's fault"
4. [n]  the quality of being inadequate or falling short of perfection; "they discussed the merits and demerits of her novel"; "he knew his own faults much better than she did"
5. [n]  (electronics) equipment failure attributable to some defect in a circuit (loose connection or insulation failure or short circuit etc.); "it took much longer to find the fault than to fix it"
6. [n]  (geology) a crack in the earth's crust resulting from the displacement of one side with respect to the other; "they built it right over a geological fault"
7. [n]  an imperfection in a device or machine; "if there are any defects you should send it back to the manufacturer"
8. [v]  put or pin the blame on

1. \Fault\, n. [OE. faut, faute, F. faute (cf. It., Sp., &
   Pg. falta), fr. a verb meaning to want, fail, freq., fr. L.
   fallere to deceive. See {Fail}, and cf. {Default}.]
   1. Defect; want; lack; default.
            One, it pleases me, for fault of a better, to call
            my friend.                            --Shak.
   2. Anything that fails, that is wanting, or that impairs
      excellence; a failing; a defect; a blemish.
            As patches set upon a little breach Discredit more
            in hiding of the fault.               --Shak.
   3. A moral failing; a defect or dereliction from duty; a
      deviation from propriety; an offense less serious than a
      crime.
   4. (Geol. & Mining)
      (a) A dislocation of the strata of the vein.
      (b) In coal seams, coal rendered worthless by impurities
          in the seam; as, slate fault, dirt fault, etc.
          --Raymond.
   5. (Hunting) A lost scent; act of losing the scent.
            Ceasing their clamorous cry till they have singled,
            With much ado, the cold fault cleary out. --Shak.
   6. (Tennis) Failure to serve the ball into the proper court.
   {At fault}, unable to find the scent and continue chase;
      hence, in trouble or embarrassment, and unable to proceed;
      puzzled; thrown off the track.
   {To find fault}, to find reason for blaming or complaining;
      to express dissatisfaction; to complain; -- followed by
      with before the thing complained of; but formerly by at.
      ``Matter to find fault at.'' --Robynson (More's Utopia).
   Syn: -- Error; blemish; defect; imperfection; weakness;
        blunder; failing; vice.
   Usage: {Fault}, {Failing}, {Defect}, {Foible}. A fault is
          positive, something morally wrong; a failing is
          negative, some weakness or falling short in a man's
          character, disposition, or habits; a defect is also
          negative, and as applied to character is the absence
          of anything which is necessary to its completeness or
          perfection; a foible is a less important weakness,
          which we overlook or smile at. A man may have many
          failings, and yet commit but few faults; or his faults
          and failings may be few, while his foibles are obvious
          to all. The faults of a friend are often palliated or
          explained away into mere defects, and the defects or
          foibles of an enemy exaggerated into faults. ``I have
          failings in common with every human being, besides my
          own peculiar faults; but of avarice I have generally
          held myself guiltless.'' --Fox. ``Presumption and
          self-applause are the foibles of mankind.''
          --Waterland.
   

2. \Fault\, v. t. [imp. & p. p. {Faulted}; p. pr. & vb. n.
   {Faulting}.]
   1. To charge with a fault; to accuse; to find fault with; to
      blame. [Obs.]
            For that I will not fault thee.       --Old Song.
   2. (Geol.) To interrupt the continuity of (rock strata) by
      displacement along a plane of fracture; -- chiefly used in
      the p. p.; as, the coal beds are badly faulted.
   

3. \Fault\, v. i.
   To err; to blunder, to commit a fault; to do wrong. [Obs.]
         If after Samuel's death the people had asked of God a
         king, they had not faulted.              --Latimer.
   

4. \Fault\, n.
   1. (Elec.) A defective point in an electric circuit due to a
      crossing of the parts of the conductor, or to contact with
      another conductor or the earth, or to a break in the
      circuit.
   2. (Geol. & Mining) A dislocation caused by a slipping of
      rock masses along a plane of facture; also, the dislocated
      structure resulting from such slipping.
   Note: The surface along which the dislocated masses have
         moved is called the
   {fault plane}. When this plane is vertical, the fault is a
   {vertical fault}; when its inclination is such that the
      present relative position of the two masses could have
      been produced by the sliding down, along the fault plane,
      of the mass on its upper side, the fault is a
   {normal}, or {gravity}, {fault}. When the fault plane is so
      inclined that the mass on its upper side has moved up
      relatively, the fault is then called a
   {reverse} (or {reversed}), {thrust}, or {overthrust},
   {fault}. If no vertical displacement has resulted, the fault
      is then called a
   {horizontal fault}. The linear extent of the dislocation
      measured on the fault plane and in the direction of
      movement is the
   {displacement}; the vertical displacement is the
   {throw}; the horizontal displacement is the
   {heave}. The direction of the line of intersection of the
      fault plane with a horizontal plane is the
   {trend} of the fault. A fault is a
   {strike fault} when its trend coincides approximately with
      the strike of associated strata (i.e., the line of
      intersection of the plane of the strata with a horizontal
      plane); it is a
   {dip fault} when its trend is at right angles to the strike;
      an
   {oblique fault} when its trend is oblique to the strike.
      Oblique faults and dip faults are sometimes called
   {cross faults}. A series of closely associated parallel
      faults are sometimes called
   {step faults} and sometimes
   {distributive faults}.
   

1. A manifestation of an error in software. A fault, if encountered, may cause a failure.

2. page fault.