Gangsta, Gangster, mobster, hood-rat. One who makes a living off of the streets and will watch his homies back, may sell drugs and/or participate in random or planned acts of violence against other "G"s and their homies.
A “G” is formally used as a “gangsta” or “gangster” but it’s becoming more common to have them as a guy or a friend. This is ainformal way to greet someone you are fairly close with. This term is more widely used among men but can be used between anyone. Make sure to only call people on your level a “G.” This term would not be used to address athourity.