What is 18 Inches Of Pain?
A very large penis about 1 foot 6 inches long and of varying girth. Said penis must be large enough to cause discomfort to a recipient in any act of sexual activity.
Daniel: Hey man, I gave THIS 18 inches of pain last night! She was screaming for mercy!
Duncan: I wish mine was 18 inches, all i have is this 1 incher...