Source : Webster's Revised Unabridged Dictionary (1913)

Patronizing \Pa"tron*i`zing\, a.
   Showing condescending favor; assuming the manner of airs of a
   superior toward another. -- {Pat"ron*i`zing*ly}, adv.
   Thackeray.

Source : WordNet®

patronizingly
     adv : with condescension; in a patronizing manner; "he treats his
           secretary condescendingly" [syn: {condescendingly}, {patronisingly}]