The Collaborative International Dictionary of English v.0.48:

Fail \Fail\, n. [OF. faille, from failir. See Fail, v. i.]
   1. Miscarriage; failure; deficiency; fault; -- mostly
      superseded by failure or failing, except in the phrase
      without fail. "His highness' fail of issue." --Shak.
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   2. Death; decease. [Obs.] --Shak.
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The Collaborative International Dictionary of English v.0.48:

Fail \Fail\, v. t.
   1. To be wanting to; to be insufficient for; to disappoint;
      to desert.
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            There shall not fail thee a man on the throne. --1
                                                  Kings ii. 4.
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   2. To miss of attaining; to lose. [R.]
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            Though that seat of earthly bliss be failed.
                                                  --Milton.
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The Collaborative International Dictionary of English v.0.48:

Fail \Fail\ (f[=a]l) v. i. [imp. & p. p. Failed (f[=a]ld); p.
   pr. & vb. n. Failing.] [F. failir, fr. L. fallere, falsum,
   to deceive, akin to E. fall. See Fail, and cf. Fallacy,
   False, Fault.]
   1. To be wanting; to fall short; to be or become deficient in
      any measure or degree up to total absence; to cease to be
      furnished in the usual or expected manner, or to be
      altogether cut off from supply; to be lacking; as, streams
      fail; crops fail.
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            As the waters fail from the sea.      --Job xiv. 11.
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            Till Lionel's issue fails, his should not reign.
                                                  --Shak.
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   2. To be affected with want; to come short; to lack; to be
      deficient or unprovided; -- used with of.
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            If ever they fail of beauty, this failure is not be
            attributed to their size.             --Berke.
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   3. To fall away; to become diminished; to decline; to decay;
      to sink.
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            When earnestly they seek
            Such proof, conclude they then begin to fail.
                                                  --Milton.
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   4. To deteriorate in respect to vigor, activity, resources,
      etc.; to become weaker; as, a sick man fails.
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   5. To perish; to die; -- used of a person. [Obs.]
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            Had the king in his last sickness failed. --Shak.
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   6. To be found wanting with respect to an action or a duty to
      be performed, a result to be secured, etc.; to miss; not
      to fulfill expectation.
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            Take heed now that ye fail not to do this. --Ezra
                                                  iv. 22.
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            Either my eyesight fails, or thou look'st pale.
                                                  --Shak.
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   7. To come short of a result or object aimed at or desired;
      to be baffled or frusrated.
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            Our envious foe hath failed.          --Milton.
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   8. To err in judgment; to be mistaken.
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            Which ofttimes may succeed, so as perhaps
            Shall grieve him, if I fail not.      --Milton.
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   9. To become unable to meet one's engagements; especially, to
      be unable to pay one's debts or discharge one's business
      obligation; to become bankrupt or insolvent; as, many
      credit unions failed in the late 1980's.
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WordNet (r) 3.0 (2006):

fail
    v 1: fail to do something; leave something undone; "She failed
         to notice that her child was no longer in his crib"; "The
         secretary failed to call the customer and the company lost
         the account" [syn: fail, neglect]
    2: be unsuccessful; "Where do today's public schools fail?";
       "The attempt to rescue the hostages failed miserably" [syn:
       fail, go wrong, miscarry] [ant: bring home the bacon,
       come through, deliver the goods, succeed, win]
    3: disappoint, prove undependable to; abandon, forsake; "His
       sense of smell failed him this time"; "His strength finally
       failed him"; "His children failed him in the crisis" [syn:
       fail, betray]
    4: stop operating or functioning; "The engine finally went";
       "The car died on the road"; "The bus we travelled in broke
       down on the way to town"; "The coffee maker broke"; "The
       engine failed on the way to town"; "her eyesight went after
       the accident" [syn: fail, go bad, give way, die,
       give out, conk out, go, break, break down]
    5: be unable; "I fail to understand your motives" [ant: bring
       off, carry off, manage, negociate, pull off]
    6: judge unacceptable; "The teacher failed six students" [ant:
       pass]
    7: fail to get a passing grade; "She studied hard but failed
       nevertheless"; "Did I fail the test?" [syn: fail, flunk,
       bomb, flush it] [ant: make it, pass]
    8: fall short in what is expected; "She failed in her
       obligations as a good daughter-in-law"; "We must not fail his
       obligation to the victims of the Holocaust"
    9: become bankrupt or insolvent; fail financially and close;
       "The toy company went bankrupt after the competition hired
       cheap Mexican labor"; "A number of banks failed that year"
    10: prove insufficient; "The water supply for the town failed
        after a long drought" [syn: fail, run out, give out]
    11: get worse; "Her health is declining"

Moby Thesaurus II by Grady Ward, 1.0:

218 Moby Thesaurus words for "fail":
   abandon, abort, age, bankrupt, be a gas, be a hit,
   be caught napping, be found wanting, be inferior, be insufficient,
   be neglectful, be negligent, be ruined, be unfaithful,
   be unsuccessful, become insolvent, bill, bomb, break, break faith,
   bust, cave in, cheat the undertaker, close down, close up,
   collapse, come apart, come short, come to grief, come unstuck,
   conk out, crash, crumble, decay, decline, decrease, default,
   deplete, desert, deteriorate, die, diminish, disappear, disappoint,
   disintegrate, disregard, dodder, drain, dramatize, droop, drop,
   dwindle, ebb, exhaust, fade, fail of, fail of success, faint, fall,
   fall away, fall flat, fall off, fall short, fall shy, fall through,
   falter, feature, fizzle out, flag, flop, flunk, flunk out, fold,
   fold up, follow, forsake, founder, get along, get on, give out,
   give way, gloss over, go back on, go bankrupt, go broke, go down,
   go downhill, go into receivership, go off, go out, go soft,
   go to pieces, go to pot, go to ruin, go under, go up, go wrong,
   grow old, gutter, have nothing on, headline, hit a slump,
   hit rock bottom, hit the skids, ignore, impoverish, jade,
   kick the beam, labor in vain, lack, lag, languish, lapse,
   leave undone, lessen, let down, let go, let ride, let slide,
   let slip, lose, lose ground, lose sight of, lose strength,
   lose track of, make a hit, melodramatize, miscarry, misfire, miss,
   mount, neglect, nod, not answer, not approach, not care for,
   not come near, not come off, not compare, not get involved,
   not hack it, not heed, not make it, not make out, not measure up,
   not pass, not qualify, not stretch, not suffice, not think,
   not work, open, open a show, overlook, pass over, pass the buck,
   peak, peg out, peter out, pine, play second fiddle, poop out,
   premiere, present, preview, produce, put on, rank under,
   reach the depths, run aground, run down, run out, run short,
   scenarize, serve, set the stage, shake, shift the blame,
   shift the responsibility, short, shrink, shrivel, shut down, sink,
   sleep, slide, slight, slip, slump, spin, stage, star, stop short,
   subserve, subside, succeed, take for granted, theatricalize,
   totter, touch bottom, try out, turn gray, turn white, wane, want,
   wash out, waste, waste away, weaken, wear away, wear thin, wilt,
   wither, wither away, wizen, worsen, wrinkle, yield