ˈcallowly,adv. [f. callow a. + -ly2.] In a callow manner; immaturely, naïvely. 1976in Conc.Oxf.Dict. (ed. 6) 141/1. 1981N.Y. Times 29 May c5/4 Callowly charismatic, the producer is a throwback to Mr. Dreyfuss' ‘Duddy Kravitz’, a man who can combine greed with guilelessness.