deadpan
dead-pan
adjective
Deliberately showing no emotion or expression, often for comedic effect.
"His deadpan delivery made the audience roar."
adverb
In a way that shows no emotion or expression, especially when being humorous.
"She delivered the witty remark deadpan."
Thesaurus
Synonyms: poker-faced, impassive, uncommunicative, incommunicative, unexpressive, expressionless