Despite what most people believe, "Base" doesn't refer to any form of Speed or Meth. Base refers to Crack Cocaine, which is the FreeBASE form of Cocaine, hence the name, "Base".
"But as the world turns I learned life is hell
Living in the world no different from a cell
Everyday I escape from Jakes givin chase, sellin base
Smokin bones in the staircase"
- Wu-Tang Clan - "C.R.E.A.M."