The Collaborative International Dictionary of English v.0.48:

Alternative \Al*ter"na*tive\, a. [Cf. F. alternatif.]
   1. Offering a choice of two things.
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   2. Disjunctive; as, an alternative conjunction.
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   3. Alternate; reciprocal. [Obs.] --Holland.
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The Collaborative International Dictionary of English v.0.48:

Alternative \Al*ter"na*tive\, n. [Cf. F. alternative, LL.
   alternativa.]
   1. An offer of two things, one of which may be chosen, but
      not both; a choice between two things, so that if one is
      taken, the other must be left.
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            There is something else than the mere alternative of
            absolute destruction or unreformed existence.
                                                  --Burke.
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   2. Either of two things or propositions offered to one's
      choice. Thus when two things offer a choice of one only,
      the two things are called alternatives.
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            Having to choose between two alternatives, safety
            and war, you obstinately prefer the worse. --Jowett
                                                  (Thucyd.).
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   3. The course of action or the thing offered in place of
      another.
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            If this demand is refused the alternative is war.
                                                  --Lewis.
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            With no alternative but death.        --Longfellow.
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   4. A choice between more than two things; one of several
      things offered to choose among.
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            My decided preference is for the fourth and last of
            these alternatives.                   --Gladstone.
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WordNet (r) 3.0 (2006):

alternative
    adj 1: serving or used in place of another; "an alternative
           plan" [syn: alternate, alternative, substitute]
    2: necessitating a choice between mutually exclusive
       possibilities; "alternative possibilities were neutrality or
       war"
    3: pertaining to unconventional choices; "an alternative life
       style"
    n 1: one of a number of things from which only one can be
         chosen; "what option did I have?"; "there no other
         alternative"; "my only choice is to refuse" [syn: option,
         alternative, choice]

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "alternative":
   additional, agent, alternate, alternate choice, analogy, another,
   attainable, backup, change, changeling, choice, comparison,
   contingency, copy, counterfeit, deputy, different, discretion,
   discretional, disjunctive, double, druthers, dummy, election,
   elective, equal, equivalent, ersatz, escape clause, escape hatch,
   exchange, exchangeable, fake, fill-in, ghost, ghostwriter,
   imitation, interchangeable, locum tenens, loophole, makeshift,
   metaphor, metonymy, mock, next best thing, option, optional,
   optionality, personnel, phony, pinch, pinch hitter, pleasure,
   possibility, possible choice, preference, pretext, provisional,
   proxy, relief, replacement, replacing, representative, reserve,
   reserves, ringer, saving clause, second string, secondary,
   selection, sign, spare, spares, stand-in, stopgap, sub,
   substituent, substitute, substitution, succedaneum, superseder,
   supplanter, surrogate, symbol, synecdoche, temporary, tentative,
   third string, token, understudy, utility, utility player, variant,
   vicar, vicarious, vice-president, vice-regent, volitional,
   voluntary, way of escape, way out, will and pleasure



Bouvier's Law Dictionary, Revised 6th Ed (1856):

ALTERNATIVE. The one or the other of two things. In contracts a party has
frequently the choice to perform one of several things, as, if he is bound
to pay one hundred dollars, or to deliver a horse, he has the alternative.
Vide Election; Obligation; Alternative.