Penis pebbles 

When a boy/man hasn't masterbated in so long his sperm becomes solid and clumps up into little pebbles.

Damn that was painful, I just ejaculated penis pebbles!

Penis pebbles by Krisuel-Blair May 28, 2008

pebble penis 

Smallest classification of penis.
Smaller than a tiny penis or micro penis.
Barely classified as a penis it is so small.
Small penile bump protruding from a male's pubic area.

"Did you bang Morris?"
"No, he had a pebble penis, it would have been impossible!"

pebble penis by blamblamglam December 10, 2013