Abbreviation for "Bukkake Goggles". More commonly called "Bug Glasses", referring to the current fashion trend in womens sunglasses.
Bukkake goggles are very large sunglasses, often (but not necessarily) round in shape, that tend to cover much of the wearers face.
BG's can be rated on a scale from 7 to 10, with 10 being extreme facial coverage. The larger the glasses, the more area to bukkake
Dood! Check out that slunt sportin' the level 10 BG's! I'm 'bout to bust a nut!