The Collaborative International Dictionary of English v.0.48:

Once \Once\ ([o^]ns), n. (Zool.)
   The ounce.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Once \Once\ (w[u^]ns), adv. [OE. ones, anes, an adverbial form
   fr. one, on, an, one. See One-, -Wards.]
   1. For one time; by limitation to the number one; not twice
      nor any number of times more than one.
      [1913 Webster]

            Ye shall . . . go round about the city once. --Josh.
                                                  vi. 3.
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            Trees that bear mast are fruitful but once in two
            years.                                --Bacon.
      [1913 Webster]

   2. At some one period of time; -- used indefinitely.
      [1913 Webster]

            My soul had once some foolish fondness for thee.
                                                  --Addison.
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            That court which we shall once govern. --Bp. Hall.
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   3. At any one time; -- often nearly equivalent to ever, if
      ever, or whenever; as, once kindled, it may not be
      quenched.
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            Wilt thou not be made clean? When shall it once be?
                                                  --Jer. xiii.
                                                  27.
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            To be once in doubt
            Is once to be resolved.               --Shak.
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   Note: Once is used as a noun when preceded by this or that;
         as, this once, that once. It is also sometimes used
         elliptically, like an adjective, for once-existing.
         "The once province of Britain." --J. N. Pomeroy.
         [1913 Webster]

   At once.
      (a) At the same point of time; immediately; without delay.
          "Stand not upon the order of your going, but go at
          once." --Shak. "I . . . withdrew at once and
          altogether." --Jeffrey.
      (b) At one and the same time; simultaneously; in one body;
          as, they all moved at once.

   Once and again, once and once more; repeatedly. "A dove
      sent forth once and again, to spy." --Milton.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ounce \Ounce\, n. [F. once; cf. It. lonza, Sp. onza; prob. for
   lonce, taken as l'once, fr. L. lynx, Gr. ?, or an (assumed)
   fem. adj. lyncea, from lynx. Cf. Lynx.] (Zool.)
   A feline quadruped (Felis irbis syn. Felis uncia)
   resembling the leopard in size, and somewhat in color, but it
   has longer and thicker fur, which forms a short mane on the
   back. The ounce is pale yellowish gray, with irregular dark
   spots on the neck and limbs, and dark rings on the body. It
   inhabits the lofty mountain ranges of Asia. Called also
   once.
   [1913 Webster] Ounded

WordNet (r) 3.0 (2006):

once
    adv 1: on one occasion; "once I ran into her" [syn: once, one
           time, in one case]
    2: as soon as; "once we are home, we can rest"
    3: at a previous time; "at one time he loved her"; "her
       erstwhile writing"; "she was a dancer once"; [syn: once,
       formerly, at one time, erstwhile, erst]

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "once":
   alone, already, ancient, anytime, anyway, anywise, apart,
   at a stroke, at all, at any time, at intervals, at once,
   at one time, at times, at whatever time, before, by itself, bygone,
   conclusively, decidedly, definitely, directly, earlier, early,
   erstwhile, finally, for good, fore, former, formerly, heretofore,
   if ever, immediately, immemorial, in a jiffy, in a trice,
   in a wink, in the singular, individually, instantly,
   just this once, late, long ago, no matter when, now and again,
   occasionally, old, olden, on one occasion, once for all,
   one by one, one day, one fine morning, one time, onetime,
   only once, particularly, past, per se, periodically, positively,
   prehistoric, previous, previously, primeval, primitive, prior,
   promptly, quondam, recent, right away, separately, severally,
   simultaneously, single-handedly, singly, singularly, some time ago,
   sometime, sometimes, sporadically, then, time was, together,
   whenever, whensoever, whilom, without delay



The Devil's Dictionary (1881-1906):

ONCE, adv.  Enough.