The Collaborative International Dictionary of English v.0.48:

Loss \Loss\ (l[o^]s; 115), n. [AS. los loss, losing, fr.
   le['i]san to lose. [root]127. See Lose, v. t.]
   1. The act of losing; failure; destruction; privation; as,
      the loss of property; loss of money by gaming; loss of
      health or reputation.
      [1913 Webster]

            Assured loss before the match be played. --Shak.
      [1913 Webster]

   2. The state of losing or having lost; the privation, defect,
      misfortune, harm, etc., which ensues from losing.
      [1913 Webster]

            Though thou repent, yet I have still the loss.
                                                  --Shak
      [1913 Webster]

   3. That which is lost or from which one has parted; waste; --
      opposed to gain or increase; as, the loss of liquor by
      leakage was considerable.
      [1913 Webster]

   4. The state of being lost or destroyed; especially, the
      wreck or foundering of a ship or other vessel.
      [1913 Webster]

   5. Failure to gain or win; as, loss of a race or battle.
      [1913 Webster]

   6. Failure to use advantageously; as, loss of time.
      [1913 Webster]

   7. (Mil.) Killed, wounded, and captured persons, or captured
      property.
      [1913 Webster]

   8. (Insurance) Destruction or diminution of value, if brought
      about in a manner provided for in the insurance contract
      (as destruction by fire or wreck, damage by water or
      smoke), or the death or injury of an insured person; also,
      the sum paid or payable therefor; as, the losses of the
      company this year amount to a million of dollars.
      [1913 Webster]

   To bear a loss, to make a loss good; also, to sustain a
      loss without sinking under it.

   To be at a loss, to be in a state of uncertainty.

   Syn: Privation; detriment; injury; damage.
        [1913 Webster]

WordNet (r) 3.0 (2006):

loss
    n 1: something that is lost; "the car was a total loss"; "loss
         of livestock left the rancher bankrupt"
    2: gradual decline in amount or activity; "weight loss"; "a
       serious loss of business"
    3: the act of losing someone or something; "everyone expected
       him to win so his loss was a shock"
    4: the disadvantage that results from losing something; "his
       loss of credibility led to his resignation"; "losing him is
       no great deprivation" [syn: loss, deprivation]
    5: the experience of losing a loved one; "he sympathized on the
       loss of their grandfather"
    6: the amount by which the cost of a business exceeds its
       revenue; "the company operated at a loss last year"; "the
       company operated in the red last year" [syn: loss, red
       ink, red] [ant: gain]
    7: military personnel lost by death or capture [syn: personnel
       casualty, loss]
    8: euphemistic expressions for death; "thousands mourned his
       passing" [syn: passing, loss, departure, exit,
       expiration, going, release]

The Free On-line Dictionary of Computing (19 January 2023):

loss

    Something (not a person) that loses; a situation in
   which something is losing.  Emphatic forms include "moby
   loss", and "total loss", "complete loss".  Common
   interjections are "What a loss!"  and "What a moby loss!"
   Note that "moby loss" is OK even though **"moby loser" is not
   used; applied to an abstract noun, moby is simply a magnifier,
   whereas when applied to a person it implies substance and has
   positive connotations.

   Compare lossage.

   (1995-04-19)


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

loss
 n.

    Something (not a person) that loses; a situation in which something is
    losing. Emphatic forms include moby loss, and total loss, complete loss.
    Common interjections are “What a loss!” and “What a moby loss!” Note that
    moby loss is OK even though **moby loser is not used; applied to an
    abstract noun, moby is simply a magnifier, whereas when applied to a person
    it implies substance and has positive connotations. Compare lossage.


The Devil's Dictionary (1881-1906):

LOSS, n.  Privation of that which we had, or had not.  Thus, in the
latter sense, it is said of a defeated candidate that he "lost his
election"; and of that eminent man, the poet Gilder, that he has "lost
his mind."  It is in the former and more legitimate sense, that the
word is used in the famous epitaph:

    Here Huntington's ashes long have lain
    Whose loss is our eternal gain,
    For while he exercised all his powers
    Whatever he gained, the loss was ours.