1. the official temporarily in charge of a diplomatic mission in the absence of the ambassador
The Collaborative International Dictionary of English v.0.48:
Charg'e d'affaires \Char`g['e]" d'af`faires"\, n.; pl.
Charg['e]s d'affaires. [F., "charged with affairs."]
A diplomatic representative, or minister of an inferior
grade, accredited by the government of one state to the
minister of foreign affairs of another; also, a substitute,
ad interim, for an ambassador or minister plenipotentiary.