Homie g means Homie gangster or even homeboy gangster. Homie means A friend or someone you grew up with basically it means your very close. Gangster means either a wanna be thug or real ones that are people behind crimes. A thug is someone who treats people in a violent way.
the definition of this word is based off them calling each other "homie" and "gangster" and putting the two together
ex: "what up gangsta", "what up homie"