As in IMprint--the outline of a guy's cock visible through his pants, shorts, or underwear; often more defined when wearing tight jeans or briefs, e.g.
The artistic product of the male pervert who climbs atop the photocopy machine naked, presses his genitals to the glass, and pushes the print button.
As the glass was clean on the photocopy machine last evening, and as it is smudged with crotch-cheese this morning, I suspect that the janitor was making Carbon cockprints all night.