Third person singular present tense of deadpan; he, she, or it delivers something with a completely expressionless face.
From 'deadpan' (expressionless delivery) plus '-s' (third person singular suffix). This allows 'deadpan' to function as a regular present-tense verb.
The simple fact that 'deadpan' transformed from a noun phrase (a dead pan/face) into both adjective and verb shows how living languages adapt vocabulary to describe cultural phenomena—comedians kept using the technique until the language needed to codify it.
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