The Collaborative International Dictionary of English v.0.48:
Diplomatically \Dip`lo*mat"ic*al*ly\, adv. According to the rules of diplomacy; in the manner of a diplomatist; artfully. [1913 Webster]WordNet (r) 3.0 (2006):
diplomatically adv 1: with diplomacy; in a diplomatic manner; "he answered very diplomatically" [ant: undiplomatically]