This is a penis that is rather girthy but short in length, similar to a tuna can. Often hard to work with while trying to have relations. Performing Doggy-Style with a woman who has 'back' is out of the question for a man sporting a 'tuna can'. The tuna can cannot enter the zone.

When you eat dirt for the first time and leave your family to build a shack in the woods

A short, but very wide human penis. It is widely accepted that one does not have intercourse with a tuna can penis, but rather uses it to punch their lover in the cunt.