The Collaborative International Dictionary of English v.0.48:

Overweening \O`ver*ween"ing\, a.
   Unduly confident; arrogant; presumptuous; conceited. --
   O`ver*ween"ingly, adv. --Milton. -- O`ver*ween"ing*ness,
   n.
   [1913 Webster]

         The conceits of warmed or overweening brain. --Locke.
   [1913 Webster]

         Here's an overweening rogue.             --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Overweening \O`ver*ween"ing\, n.
   Conceit; arrogance. --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

overweening
    adj 1: unrestrained, especially with regard to feelings;
           "extravagant praise"; "exuberant compliments";
           "overweening ambition"; "overweening greed" [syn:
           excessive, extravagant, exuberant, overweening]
    2: presumptuously arrogant; "had a witty but overweening
       manner"; "no idea how overweening he would be"- S.V.Benet;
       "getting a little uppity and needed to be slapped down"- NY
       Times [syn: overweening, uppity]

Moby Thesaurus II by Grady Ward, 1.0:

133 Moby Thesaurus words for "overweening":
   a bit much, abandoned, arrogant, assuming, assured, audacious,
   boundless, brash, brazen, brazenfaced, bumptious, cocksure, cold,
   complacent, confident, consequential, contumelious, convinced,
   cool, decided, determined, disdainful, egregious, enormous,
   exaggerated, excessive, exorbitant, extravagant, extreme, fabulous,
   familiar, fancy, forward, gigantic, gluttonous, high, hubristic,
   hyperbolic, hypertrophied, immoderate, improvident, imprudent,
   impudent, incautious, incontinent, indiscreet, injudicious,
   inordinate, insolent, insulting, intemperate, monstrous, narcissan,
   narcissine, narcissistic, narcistic, obtrusive, out of bounds,
   out of sight, outrageous, overbig, overbold, overcareless,
   overconfident, overdeveloped, overgreat, overgrown, overlarge,
   overmuch, overpresumptuous, overproud, oversure, persuaded, poised,
   pompous, positive, presuming, presumptuous, procacious, proud,
   pushful, pushy, rash, reassured, secure, self-admiring,
   self-appointed, self-approving, self-asserting, self-assertive,
   self-assuming, self-assured, self-complacent, self-confident,
   self-congratulating, self-congratulatory, self-content,
   self-contented, self-delighting, self-elect, self-endeared,
   self-esteeming, self-gratulating, self-gratulatory, self-important,
   self-loving, self-reliant, self-respecting, self-satisfied,
   self-sufficient, smug, steep, stiff, sure, temerarious, too much,
   unafraid, unbridled, unchary, unconscionable, undoubting, undue,
   unfaltering, unhesitating, unreasonable, unrestrained, unwary,
   unwavering, uppish, uppity, vain, vainglorious, would-be