The Collaborative International Dictionary of English v.0.48:
Diplomatist \Di*plo"ma*tist\, n. [Cf. F. diplomatiste a student of diplomatics.] A person employed in, or skilled in, diplomacy; a diplomat. [1913 Webster] In ability, Avaux had no superior among the numerous able diplomatists whom his country then possessed. --Macaulay. DiplopiaWordNet (r) 3.0 (2006):
diplomatist n 1: an official engaged in international negotiations [syn: diplomat, diplomatist]