1. When a female to male transexual opts for scrotoplasty as opposed to having a penis constructed while also retaining their vagina.

2. When eating a tuna sub, the tuna sac is the tuna that falls out of the sub and into the paper used to wrap the sandwich for convenient eating. Tuna sacs of this sort are often moist.
1. I though last nights hook-up was fittin' to be dope, but I couldn't get past the tuna sack.

2. Shit, this sandwich was great, but now it has a tuna sack.
by Tuna sack enthusiast. June 19, 2011
Get the Tuna Sack mug.