DEADPAN

[adjective], [adverb] - without expressing any feelings; without emotionsHer deadpan face really fooled me when she said she'd lost my bag - I didn't realize she was joking.Their deadpan humour/wit is too subtle for some audiences.The deadpan tone of the police report did not reflect the full horror of the accident."Come any closer and I'll shoot," she said, completely deadpan.