Stupefy

[Jason Yan]

To make stupid; to make dull; to blunt the faculty of
perception or understanding in; to deprive of sensibility; to make
torpid.

[Dave Paprocki]

A spell in [the Harry Potter series] of books, used to [stun] your opponent in a duel. This is a common spell that Harry Potter uses, especially when fighting You Know Whos [death eaters] in the 5th 6th and 7th Potter books.

[Renato]

Make (someone) unable to think or feel properly.

[Raeanne Dimick]

A term used in moments of hilarity, complete [randomness], or [hyperness]. You point [weirdly] at your friends, acquaintances, teachers or complete strangers and say Stupefy! in a silly voice, thus causing much laughter.