All Head, No Shaft 

Analogous to "All Bark, No Bite". A person who is a loud, obnoxious, overly aggressive jackass, but without anything to back up the behavior. It's is like having a thick two-inch dick with a huge head, impressive to the owner but basically useless.

"Look at this feeble dork acting hard and trying to boss everyone around;

He's All Head, No Shaft."

All Head, No Shaft by Tabooky February 4, 2009

all head and no shaft 

A very sad penis with a giant helmet and no neck. aka Mushroom tip. GNome hat or bridget the midget.

Carla; Josh is all head and no shaft.
bianca: You'd been better off getting a butt plug

all head and no shaft by Bluvelvet72 July 27, 2018