Source : Webster's Revised Unabridged Dictionary (1913)

Debonair \Deb`o*nair"\, a. [OE. debonere, OF. de bon aire,
   debonaire, of good descent or lineage, excellent, debonair,
   F. d['e]bonnaire debonair; de of (L. de) + bon good (L.
   bonus) + aire. See {Air}, and {Bounty}, and cf. {Bonair}.]
   Characterized by courteousness, affability, or gentleness; of
   good appearance and manners; graceful; complaisant.

         Was never prince so meek and debonair.   --Spenser.

Source : WordNet®

debonair
     adj 1: having a sophisticated charm; "a debonair gentleman" [syn: {debonaire},
             {debonnaire}, {suave}]
     2: having a cheerful, lively, and self-confident air; "looking
        chipper, like a man...diverted by his own wit"- Frances G.
        Patton; "life that is gay, brisk, and debonair"-
        H.M.Reynolds; "walked with a jaunty step"; "a jaunty
        optimist" [syn: {chipper}, {debonaire}, {jaunty}]