The Collaborative International Dictionary of English v.0.48:

Now \Now\ (nou), adv. [OE. nou, nu, AS. n[=u], nu; akin to D.,
   OS., & OHG. nu, G. nu, nun, Icel., n[=u], Dan., Sw., & Goth.
   nu, L. nunc, Gr. ny`, ny^n, Skr. nu, n[=u]. [root]193. Cf.
   New.]
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   1. At the present time; at this moment; at the time of
      speaking; instantly; as, I will write now.
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            I have a patient now living, at an advanced age, who
            discharged blood from his lungs thirty years ago.
                                                  --Arbuthnot.
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   2. Very lately; not long ago.
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            They that but now, for honor and for plate,
            Made the sea blush with blood, resign their hate.
                                                  --Waller.
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   3. At a time contemporaneous with something spoken of or
      contemplated; at a particular time referred to.
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            The ship was now in the midst of the sea. --Matt.
                                                  xiv. 24.
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   4. In present circumstances; things being as they are; --
      hence, used as a connective particle, to introduce an
      inference or an explanation.
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            How shall any man distinguish now betwixt a parasite
            and a man of honor?                   --L'Estrange.
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            Why should he live, now nature bankrupt is? --Shak.
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            Then cried they all again, saying, Not this man, but
            Barabbas. Now, Barabbas was a robber. --John xviii.
                                                  40.
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            The other great and undoing mischief which befalls
            men is, by their being misrepresented. Now, by
            calling evil good, a man is misrepresented to others
            in the way of slander.                --South.
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   Now and again, now and then; occasionally.

   Now and now, again and again; repeatedly. [Obs.] --Chaucer.

   Now and then, at one time and another; indefinitely;
      occasionally; not often; at intervals. "A mead here, there
      a heath, and now and then a wood." --Drayton.

   Now now, at this very instant; precisely now. [Obs.] "Why,
      even now now, at holding up of this finger, and before the
      turning down of this." --J. Webster (1607).

   Now . . . now, alternately; at one time . . . at another
      time. "Now high, now low, now master up, now miss."
      --Pope.
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The Collaborative International Dictionary of English v.0.48:

Now \Now\, a.
   Existing at the present time; present. [R.] "Our now
   happiness." --Glanvill.
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The Collaborative International Dictionary of English v.0.48:

Now \Now\, n.
   The present time or moment; the present.
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         Nothing is there to come, and nothing past;
         But an eternal now does ever last.       --Cowley.
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WordNet (r) 3.0 (2006):

now
    adv 1: in the historical present; at this point in the narration
           of a series of past events; "President Kennedy now calls
           in the National Guard"; "Washington now decides to cross
           the Delaware"; "the ship is now listing to port"
    2: in these times; "it is solely by their language that the
       upper classes nowadays are distinguished"- Nancy Mitford; "we
       now rarely see horse-drawn vehicles on city streets"; "today
       almost every home has television" [syn: nowadays, now,
       today]
    3: used to preface a command or reproof or request; "now hear
       this!"; "now pay attention"
    4: at the present moment; "goods now on sale"; "the now-aging
       dictator"; "they are now abroad"; "he is busy at present
       writing a new novel"; "it could happen any time now" [syn:
       now, at present]
    5: without delay or hesitation; with no time intervening; "he
       answered immediately"; "found an answer straightaway"; "an
       official accused of dishonesty should be suspended
       forthwith"; "Come here now!" [syn: immediately,
       instantly, straightaway, straight off, directly,
       now, right away, at once, forthwith, like a shot]
    6: (prefatory or transitional) indicates a change of subject or
       activity; "Now the next problem is..."
    7: in the immediate past; "told me just now"
    n 1: the momentary present; "Now is a good time to do it"; "it
         worked up to right now"