マジボケ

noun

unintentionally comedic stupidity; serious-faced blunder

Slang for when someone says or does something foolish with a straight face, making it unintentionally funny. Often used in comedy contexts.

• 彼かれのマジボケには、つい笑わらってしまった。

  I couldn't help laughing at his unintentionally comedic stupidity.

• あの芸げい人にんはマジボケが得とく意いだ。

  That comedian is good at deadpan blunders.