Bell Labs, the research and development arm of Bell System

Better Than Life, a video game in the Red Dwarf television series

Buy to let, an investment strategy

Bridge-tied load, an output configuration for amplifiers

Biomass to liquid, synthesized liquid fuels made out of biomass

Belize Telecommunications Limited, a Belizean telecommunications company

Below the line, a phrase with several meanings

Battle Creek (Amtrak station), Amtrak station code BTL