In a manner befitting an ambassador, with diplomatic courtesy, formal dignity, and official propriety.
From 'ambassadorial' plus the suffix '-ly' (in a manner of), creating an adverb that describes how something is done with ambassador-like qualities.
This is a word you'd use when describing someone who handles a tense situation with grace and diplomacy—they didn't lose their temper or say something rude, they responded ambassadorially!
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