Deadpan

Deadpan is a form of comic delivery in which humor is presented without a change in emotion or body language, usually speaking in a casual, monotone, solemn, blunt, disgusted or matter-of-fact voice and expressing an unflappably calm, archly insincere or artificially grave demeanor. This delivery is also called dry wit when the intent, but not the presentation, is humorous, oblique, sarcastic or apparently unintentional.