The Collaborative International Dictionary of English v.0.48:

zany \za"ny\ (z[=a]"n[-e]), adj.
   Comical in a clownish or buffoonish manner; whimsically
   comical.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Zany \Za"ny\, n.; pl. Zanies. [It. zanni a buffoon,
   merry-andrew, orig. same as Giovanni John, i. e., merry John,
   L. Ioannes, Gr. ?, Heb. Y[=o]kh[=a]n[=a]n, prop., the Lord
   graciously gave: cf. F. zani, fr. the Italian. Cf.
   Jenneting.]
   A merry-andrew; a buffoon.
   [1913 Webster]

         Then write that I may follow, and so be
         Thy echo, thy debtor, thy foil, thy zany. --Donne.
   [1913 Webster]

         Preacher at once, and zany of thy age.   --Pope.
   [1913 Webster]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Zany \Za"ny\, v. t.
   To mimic. [Obs.]
   [1913 Webster]

         Your part is acted; give me leave at distance
         To zany it.                              --Massinger.
   [1913 Webster]

WordNet (r) 3.0 (2006):

zany
    adj 1: ludicrous, foolish; "gave me a cockamamie reason for not
           going"; "wore a goofy hat"; "a silly idea"; "some wacky
           plan for selling more books" [syn: cockamamie,
           cockamamy, goofy, sappy, silly, wacky,
           whacky, zany]
    2: like a clown; "a buffoonish walk"; "a clownish face"; "a zany
       sense of humor" [syn: buffoonish, clownish, clownlike,
       zany]
    n 1: a buffoon in one of the old comedies; imitates others for
         ludicrous effect
    2: a man who is a stupid incompetent fool [syn: fathead,
       goof, goofball, bozo, jackass, goose, cuckoo,
       twat, zany]

The Devil's Dictionary (1881-1906):

ZANY, n.  A popular character in old Italian plays, who imitated with
ludicrous incompetence the _buffone_, or clown, and was therefore the
ape of an ape; for the clown himself imitated the serious characters
of the play.  The zany was progenitor to the specialist in humor, as
we to-day have the unhappiness to know him.  In the zany we see an
example of creation; in the humorist, of transmission.  Another
excellent specimen of the modern zany is the curate, who apes the
rector, who apes the bishop, who apes the archbishop, who apes the
devil.