___-dial (make an accidental cellphone call) (4)

I believe the answer is:

butt

(Other definitions for butt that I've seen before include "Strike with head" , "Target < vessel" , "Knock head" , "Hit with the head; object of ridicule" , "Blunt end - target of ridicule - hit with the head - cask - US backside" .)

I've seen this clue in the Universal.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.