The Collaborative International Dictionary of English v.0.48:

Forfeit \For"feit\, n. [OE. forfet crime, penalty, F. forfait
   crime (LL. forefactum, forifactum), prop. p. p. of forfaire
   to forfeit, transgress, fr. LL. forifacere, prop., to act
   beyond; L. foris out of doors, abroad, beyond + facere to do.
   See Foreign, and Fact.]
   1. Injury; wrong; mischief. [Obs. & R.]
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            To seek arms upon people and country that never did
            us any forfeit.                       --Ld. Berners.
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   2. A thing forfeit or forfeited; what is or may be taken from
      one in requital of a misdeed committed; that which is
      lost, or the right to which is alienated, by a crime,
      offense, neglect of duty, or breach of contract; hence, a
      fine; a mulct; a penalty; as, he who murders pays the
      forfeit of his life.
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            Thy slanders I forgive; and therewithal
            Remit thy other forfeits.             --Shak.
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   3. Something deposited and redeemable by a sportive fine; --
      whence the game of forfeits.
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            Country dances and forfeits shortened the rest of
            the day.                              --Goldsmith.
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The Collaborative International Dictionary of English v.0.48:

Forfeit \For"feit\, v. i.
   1. To be guilty of a misdeed; to be criminal; to transgress.
      [Obs.]
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   2. To fail to keep an obligation. [Obs.]
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            I will have the heart of him if he forfeit. --Shak.
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The Collaborative International Dictionary of English v.0.48:

Forfeit \For"feit\, p. p. or a.
   In the condition of being forfeited; subject to alienation.
   --Shak.
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         Once more I will renew
         His laps[`e]d powers, though forfeite.   --Milton.
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The Collaborative International Dictionary of English v.0.48:

Forfeit \For"feit\, a. [F. forfait, p. p. of forfaire. See
   Forfeit, n.]
   Lost or alienated for an offense or crime; liable to penal
   seizure.
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         Thy wealth being forfeit to the state.   --Shak.
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         To tread the forfeit paradise.           --Emerson.
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The Collaborative International Dictionary of English v.0.48:

Forfeit \For"feit\, v. t. [imp. & p. p. Forfeited; p. pr. &
   vb. n. Forfeiting.] [OE. forfeten. See Forfeit, n.]
   To lose, or lose the right to, by some error, fault, offense,
   or crime; to render one's self by misdeed liable to be
   deprived of; to alienate the right to possess, by some
   neglect or crime; as, to forfeit an estate by treason; to
   forfeit reputation by a breach of promise; -- with to before
   the one acquiring what is forfeited.
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         [They] had forfeited their property by their crimes.
                                                  --Burke.
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         Undone and forfeited to cares forever!   --Shak.
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WordNet (r) 3.0 (2006):

forfeit
    adj 1: surrendered as a penalty [syn: confiscate, forfeit,
           forfeited]
    n 1: something that is lost or surrendered as a penalty; [syn:
         forfeit, forfeiture]
    2: a penalty for a fault or mistake that involves losing or
       giving up something; "the contract specified forfeits if the
       work was not completed on time" [syn: forfeit,
       forfeiture]
    3: the act of losing or surrendering something as a penalty for
       a mistake or fault or failure to perform etc. [syn:
       forfeit, forfeiture, sacrifice]
    v 1: lose (s.th.) or lose the right to (s.th.) by some error,
         offense, or crime; "you've forfeited your right to name
         your successor"; "forfeited property" [syn: forfeit,
         give up, throw overboard, waive, forgo, forego]
         [ant: arrogate, claim, lay claim]