AC/DC stands for Alternating Current/Direct Current. This label was found, long ago, on machines that could run on either sort of power. These days you only get DC from batteries and the like; all wall sockets use AC. Nowadays all AC/DC appliances actually run on battery power, but have an AC/DC converter included so that they can also be plugged into wall sockets. The band AC/DC took their name from the AC/DC label on the back of a sewing machine. They thought that it represented the band's energy and exciting performances, and they have done quite well with that name.

What about those who swing both ways? AC-DC's?
-- Beck, Where It's At

Unbeknownst to the band members, AC/DC has long been a slang term for a bisexual person -- reported to be in use as far back as the 1940s. No one seems to know where the slang usage started, but it no doubt comes from the same electronic origins as does the band's name. An AC/DC is a person that can 'run' on either male or female 'energy'. The metaphor is weak, but the term has survived for 60 years, so apparently it has something going for it.