The Collaborative International Dictionary of English v.0.48:

another \an*oth"er\ ([a^]n*[u^][th]"[~e]r), pron. & a. [An a,
   one + other.]
   1. One more, in addition to a former number; a second or
      additional one, similar in likeness or in effect.
      [1913 Webster]

            Another yet! -- a seventh! I 'll see no more.
                                                  --Shak.
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            Would serve to scale another Hero's tower. --Shak.
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   2. Not the same; different.
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            He winks, and turns his lips another way. --Shak.
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   3. Any or some; any different person, indefinitely; any one
      else; some one else.
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            Let another man praise thee, and not thine own
            mouth.                                --Prov. xxvii.
                                                  2.
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            While I am coming, another steppeth down before me.
                                                  --John v. 7.
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   Note: As a pronoun another may have a possessive another's,
         pl. others, poss. pl. other'. It is much used in
         opposition to one; as, one went one way, another
         another. It is also used with one, in a reciprocal
         sense; as, "love one another," that is, let each love
         the other or others. "These two imparadised in one
         another's arms." --Milton.
         [1913 Webster]

WordNet (r) 3.0 (2006):

another
    adj 1: any of various alternatives; some other; "put it off to
           another (or some other) day" [syn: another(a), some
           other]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "another":
   accessory, added, additional, ancillary, autre chose, auxiliary,
   collateral, contributory, different story, different thing, else,
   extra, farther, fresh, further, more, new, no such thing,
   not that sort, not the same, not the type, of a sort,
   of another sort, of sorts, other, other than, otherwise, peculiar,
   plus, quite another thing, rare, renewed, second, something else,
   something else again, spare, special, sui generis, supernumerary,
   supplemental, supplementary, surplus, that, ulterior, unique