1. Substance D is a fictional addictive amphetamine-
like psychoactive drug, also known as "Slow Death", "Death" and "D", that is depicted in
Philip K. Dick's novel "A Scanner Darkly". It's derived from the fictional
flower "Mors ontologica".
2. By extension, Substance D can refer to amphetamine (speed).
"What he sold me as '
candy' actually turned out to be 'Substance D'."
This is a more subtle way to refer to amphetamine in a conversation if you
don'
t want to attract too much attention.