synonymous with, and possibly a contraction of "Blows" (not to be confused with "Blow").
It is usually used to describe the most prevalent local variety of heroin, which is often presented as a mixture of 16-35% diacetylmorphine, ~15% mannose (sometimes lactose), 20-30% quinine hcl, and diphenhydramine or cimetadine. The latter three of these excipient ingredients are understood to function as antihistamines, anti-catabolic potentiators, and "taste-imitators".
The word can also be used in it's verb form to refer to the act of self-administration. e.g., to "get low"
"Yo mang, we f**king Aced that Laplacian Electrostatics final! We should celebrate seven thirty mang."
"we should get low as f**k. lets hit the trap--ima call mah boy an let him know it's a bill eighty."
"oh snap, thas like 22 bags of low. lets smash out!"