Definition

A deliberately annoying one-word response tactic that forces someone to repeat themselves, either to derail a boring conversation or dodge an awkward question. The more clearly they originally spoke, the more infuriating and hilarious this becomes.

Example Usage

My mom asked when I'd clean my room, so I hit her with 'What?' three times until she gave up.

Source: Urban Dictionary (https://www.urbandictionary.com/define.php?term=What%3F&defid=18740688)