The Collaborative International Dictionary of English v.0.48:

Lose \Lose\ (l[=oo]z), v. t. [imp. & p. p. Lost (l[o^]st; 115)
   p. pr. & vb. n. Losing (l[=oo]z"[i^]ng).] [OE. losien to
   loose, be lost, lose, AS. losian to become loose; akin to OE.
   leosen to lose, p. p. loren, lorn, AS. le['i]san, p. p. loren
   (in comp.), D. verliezen, G. verlieren, Dan. forlise, Sw.
   f["o]rlisa, f["o]rlora, Goth. fraliusan, also to E. loose, a
   & v., L. luere to loose, Gr. ly`ein, Skr. l[=u] to cut.
   [root]127. Cf. Analysis, Palsy, Solve, Forlorn,
   Leasing, Loose, Loss.]
   [1913 Webster]
   1. To part with unintentionally or unwillingly, as by
      accident, misfortune, negligence, penalty, forfeit, etc.;
      to be deprived of; as, to lose money from one's purse or
      pocket, or in business or gaming; to lose an arm or a leg
      by amputation; to lose men in battle.
      [1913 Webster]

            Fair Venus wept the sad disaster
            Of having lost her favorite dove.     --Prior.
      [1913 Webster]

   2. To cease to have; to possess no longer; to suffer
      diminution of; as, to lose one's relish for anything; to
      lose one's health.
      [1913 Webster]

            If the salt hath lost his savor, wherewith shall it
            be salted?                            --Matt. v. 13.
      [1913 Webster]

   3. Not to employ; to employ ineffectually; to throw away; to
      waste; to squander; as, to lose a day; to lose the
      benefits of instruction.
      [1913 Webster]

            The unhappy have but hours, and these they lose.
                                                  --Dryden.
      [1913 Webster]

   4. To wander from; to miss, so as not to be able to and; to
      go astray from; as, to lose one's way.
      [1913 Webster]

            He hath lost his fellows.             --Shak
      [1913 Webster]

   5. To ruin; to destroy; as destroy; as, the ship was lost on
      the ledge.
      [1913 Webster]

            The woman that deliberates is lost.   --Addison.
      [1913 Webster]

   6. To be deprived of the view of; to cease to see or know the
      whereabouts of; as, he lost his companion in the crowd.
      [1913 Webster]

            Like following life thro' creatures you dissect,
            You lose it in the moment you detect. --Pope.
      [1913 Webster]

   7. To fail to obtain or enjoy; to fail to gain or win; hence,
      to fail to catch with the mind or senses; to miss; as, I
      lost a part of what he said.
      [1913 Webster]

            He shall in no wise lose his reward.  --Matt. x. 42.
      [1913 Webster]

            I fought the battle bravely which I lost,
            And lost it but to Macedonians.       --Dryden.
      [1913 Webster]

   8. To cause to part with; to deprive of. [R.]
      [1913 Webster]

            How should you go about to lose him a wife he loves
            with so much passion?                 --Sir W.
                                                  Temple.
      [1913 Webster]

   9. To prevent from gaining or obtaining.
      [1913 Webster]

            O false heart! thou hadst almost betrayed me to
            eternal flames, and lost me this glory. --Baxter.
      [1913 Webster]

   To lose ground, to fall behind; to suffer gradual loss or
      disadvantage.

   To lose heart, to lose courage; to become timid. "The
      mutineers lost heart." --Macaulay.

   To lose one's head, to be thrown off one's balance; to lose
      the use of one's good sense or judgment, through fear,
      anger, or other emotion.
      [1913 Webster]

            In the excitement of such a discovery, many scholars
            lost their heads.                     --Whitney.

   To lose one's self.
      (a) To forget or mistake the bearing of surrounding
          objects; as, to lose one's self in a great city.
      (b) To have the perceptive and rational power temporarily
          suspended; as, we lose ourselves in sleep.

   To lose sight of.
      (a) To cease to see; as, to lose sight of the land.
      (b) To overlook; to forget; to fail to perceive; as, he
          lost sight of the issue.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lose \Lose\, v. i.
   To suffer loss, disadvantage, or defeat; to be worse off,
   esp. as the result of any kind of contest.
   [1913 Webster]

         We 'll . . . hear poor rogues
         Talk of court news; and we'll talk with them too,
         Who loses and who wins; who's in, who's out. --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lose
    v 1: fail to keep or to maintain; cease to have, either
         physically or in an abstract sense; "She lost her purse
         when she left it unattended on her seat" [ant: hold on,
         keep]
    2: fail to win; "We lost the battle but we won the war" [ant:
       win]
    3: suffer the loss of a person through death or removal; "She
       lost her husband in the war"; "The couple that wanted to
       adopt the child lost her when the biological parents claimed
       her"
    4: place (something) where one cannot find it again; "I
       misplaced my eyeglasses" [syn: misplace, mislay, lose]
    5: miss from one's possessions; lose sight of; "I've lost my
       glasses again!" [ant: find, regain]
    6: allow to go out of sight; "The detective lost the man he was
       shadowing after he had to stop at a red light"
    7: fail to make money in a business; make a loss or fail to
       profit; "I lost thousands of dollars on that bad
       investment!"; "The company turned a loss after the first
       year" [syn: lose, turn a loss] [ant: break even,
       profit, turn a profit]
    8: fail to get or obtain; "I lost the opportunity to spend a
       year abroad" [ant: acquire, gain, win]
    9: retreat [syn: fall back, lose, drop off, fall behind,
       recede] [ant: advance, gain, gain ground, get
       ahead, make headway, pull ahead, win]
    10: fail to perceive or to catch with the senses or the mind; "I
        missed that remark"; "She missed his point"; "We lost part
        of what he said" [syn: miss, lose]
    11: be set at a disadvantage; "This author really suffers in
        translation" [syn: suffer, lose]

Moby Thesaurus II by Grady Ward, 1.0:

80 Moby Thesaurus words for "lose":
   be bereaved of, be found wanting, be unsuccessful, bereave,
   bite the dust, bow, bow to, capitulate, clear, come to grief,
   consume, decline, default, disinherit, displace, dispossess,
   dissipate, divest, draw a blank, drop, elude, escape, evade,
   exhaust, expend, fail, fail of success, fall, flunk, flunk out,
   forfeit, forget, fritter away, give the slip, give up,
   go astray from, go bankrupt, go down, go under, have enough,
   incur loss, kiss good-bye, labor in vain, let slip, lick the dust,
   lose out, lose sight of, lose the day, mislay, misplace, miss,
   not come off, not pass, not remember, not work, oust, part with,
   relinquish, rid, rob, sacrifice, say uncle, shake off, slip, spend,
   spill, squander, succumb, suffer loss, surrender, take the count,
   throw off, trifle away, tumble, unburden, undergo privation,
   use up, wander from, waste, yield



The Jargon File (version 4.4.7, 29 Dec 2003):

lose
 vi.

    1. [very common] To fail. A program loses when it encounters an exceptional
    condition or fails to work in the expected manner.

    2. To be exceptionally unesthetic or crocky.

    3. Of people, to be obnoxious or unusually stupid (as opposed to ignorant).
    See also deserves to lose.

    4. n. Refers to something that is losing, especially in the phrases ?
    That's a lose!? and ?What a lose!?


The Free On-line Dictionary of Computing (30 December 2018):

lose

    (MIT) 1. To fail.  A program loses when it
   encounters an exceptional condition or fails to work in the
   expected manner.

   2. To be exceptionally unesthetic or crocky.

   3. Of people, to be obnoxious or unusually stupid (as opposed
   to ignorant).

   4. Refers to something that is losing, especially in the
   phrases "That's a lose!" and "What a lose!"

   [Jargon File]

   (1995-04-19)