When there are two males and one female, the female first gives oral to the first male. Who ejaculates in her mouth. The female keeps it in her mouth while giving oral to the second male. Effectively coating his dick like a dilly bar.
The small to large portion of skin on your lower back that is exposed when the shirt does not meet the pants. caused by too short a shirt, low pants, bending over or a combination of the three.
"oh man did you see the Dilly Bar on that girl when she bent down to pick up her pencil??"
or
"oh my gosh jen get a belt! your dilly bar is showing"