An evolution of the turtlehead. A hammerhead occurs when the turtles head is squashed between your butt cheeks into a boomerang style shape not disimilar to the head of the afformentioned hammerhead shark.
Reg was taking a dump when the fire alarm went off. He jumped to his feet, buttocks tensed and then realised he had given himself a massive hammerhead.
by craftyscouser March 21, 2011
The name for what your penis looks like when only the head of the penis fills with blood and you don't actually have an erection. It could happen when sitting down and then standing up quickly or anytime.
by jive robots November 03, 2010
by snorker Major June 29, 2013
In the process of getting road head on the highway, you drift your car over to the side and begin hitting every bit of rumble strip that you can find. Thus creating a vibrating sensation know as hammerhead.
When the road head just wasn't enough to get off, Johnny used the rumble strips of the highway to get hammerhead.
by bkrazy November 17, 2006
Derisive nickname used by my boyfriend when I do something ditzy - a reference to the term "dumb as a bag of hammers."
Nice move, hammerhead.
by Blonder by the minute January 20, 2004
When a rectangular object is placed sideways under the foreskin, making the penis resemble a hammerhead shark.
A kinky girl i am seeing put a domino in my foreskin last night, it made my cock look like a hammerhead shark.
by bosteonerbeka March 23, 2010
Most fratboys lock themselves in their giant houses and chase one another with their pants off to give each other wicked hammerheads.
by lankysob November 23, 2005