What is G-banger?
1.
Aussie slang for "G-string" or "thong".
Someone would see a woman wearing a G-string and whistle and say to his mates "Hey guys, check that chick out, she's wearing a G-banger".
See
2.
a small peice of material held between the buttocks. commonly used to avoid the VPL (visible panty line)
A certain tennis player likes to "tweek his g-banger" on the court.
See