When one's scrotum sticks to the inner thighs due to sweating in the groin area. This situation can be nicknamed 'Batwings' because the image created by this scenario can resemble a bat and its wings. The shaft of the penis can be see as the body and the stretched scrotum to either side can be seen as the wings. Many males (and hermaphrodites) find this common occasion displeasing.

When the mans scrotum is hot and sweaty and stuck together to the his ass or thigh.

when your sack sticks to both legs

When you stretch the extra skin betwen your balls out far and flat, like a sheet of paper. So you can see the veins and everything, like a batwing.

when you stretch out your ballsack like paper, then get another man to inadvertently look at it. This is followed by the ballsack exposer calling the looker gay and kicking him in the ass twice.

when you get real sweaty and your ball sack sticks to your legs and you spread them.

The excess skin of your ballbag when it sticks to your inner leg on a hot day. When spreading your legs the skin streches and looks like a Batwing! All veiny and stuff!