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]