The definition of a G Pack or G-Pack is:
$1,000 dollars worth of any street drug: Cocaine, Crack Cocaine, Heroin, and Crack. etc.
Hence the (G) in G-pack. A G is a grand, a grand is $1000 dollars. And (pack) is reffering to a pack of street drugs.
The average street/corner drug dealer works with a G Pack, I would say 96% percent of corner dealers work with g packs. 2% percent work with higher ammounts and 2% percent work with lower ammounts.
50 Cent- Position of Power: My niggas with g-packs, selling out on the hour, they shoot when I say shoot, so I'm in a position of power....you fuck around if you wanna.