The Collaborative International Dictionary of English v.0.48:

Passant \Pas"sant\, a. [F., p. pr. of passer. See Pass, v. i.]
   1. Passing from one to another; in circulation; current.
      [Obs.]
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            Many opinions are passant.            --Sir T.
                                                  Browne.
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   2. Curs?ry, careless. [Obs.]
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            On a passant rewiew of what I wrote to the bishop.
                                                  --Sir P. Pett.
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   3. Surpassing; excelling. [Obs.] --Chaucer.
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   4. (Her.) Walking; -- said of any animal on an escutcheon,
      which is represented as walking with the dexter paw
      raised.
      [1913 Webster] Passe
      passe