The Collaborative International Dictionary of English v.0.48:

Again \A*gain"\, Agains \A*gains"\, prep.
   Against; also, towards (in order to meet). [Obs.]
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         Albeit that it is again his kind.        --Chaucer.
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The Collaborative International Dictionary of English v.0.48:

Again \A*gain"\ (?; 277), adv. [OE. agein, agayn, AS. ongegn,
   onge['a]n, against, again; on + ge['a]n, akin to Ger. gegewn
   against, Icel. gegn. Cf. Gainsay.]
   1. In return, back; as, bring us word again.
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   2. Another time; once more; anew.
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            If a man die, shall he live again?    --Job xiv. 14.
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   3. Once repeated; -- of quantity; as, as large again, half as
      much again.
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   4. In any other place. [Archaic] --Bacon.
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   5. On the other hand. "The one is my sovereign . . . the
      other again is my kinsman." --Shak.
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   6. Moreover; besides; further.
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            Again, it is of great consequence to avoid, etc.
                                                  --Herschel.
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   Again and again, more than once; often; repeatedly.

   Now and again, now and then; occasionally.

   To and again, to and fro. [Obs.] --De Foe.
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   Note: Again was formerly used in many verbal combinations,
         as, again-witness, to witness against; again-ride, to
         ride against; again-come, to come against, to
         encounter; again-bring, to bring back, etc.
         [1913 Webster] Again

WordNet (r) 3.0 (2006):

again
    adv 1: anew; "she tried again"; "they rehearsed the scene again"
           [syn: again, once again, once more, over again]

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "again":
   ab ovo, above, additionally, afresh, after all, albeit,
   all included, all the same, also, although, altogether,
   among other things, and all, and also, and so, anew, anon,
   another time, around, as new, as well, at all events,
   at another time, at any rate, at that moment, at that time,
   au reste, back, backward, beside, besides, beyond, bis, but,
   compare, contra, contrariwise, contrary, contrawise, conversely,
   da capo, de novo, ditto, else, en plus, encore, even, even so,
   extra, farther, for all that, for lagniappe, freshly, from scratch,
   from the beginning, howbeit, however, in addition, in any case,
   in any event, in reverse, in that case, inter alia,
   into the bargain, item, just the same, likewise, more, moreover,
   nevertheless, new, newly, nonetheless, notwithstanding,
   on that occasion, on the side, on top of, once again, once more,
   oppositely, over, over again, plus, rather, round, round about,
   similarly, still, then, thereat, therewith, though, to boot, too,
   twice over, two times, vice versa, when, yet, yet again