What is a "SHOTGUN" speaker cable??

Gosh- here is what I think:

An internal bi-wire has a single connection at the amp end and a double connection at the speaker end all housed in a single cable.

An external bi-wire or "shotgun" cable has two separate runs of cable with a single connection (a '+' & a '-') at the amp end and each separate run of cable has a '+' & '-' at the speaker end. So you have four runs of cable total. If you break the single connection at the amp end you could single wire two sets of speakers.

I think the term external biwire is aptly descriptive. Where the term "shotgun" came from is anybody's guess.

Jig has it right. The mad milkman has it wrong.
Example: Kimber 8tc has eight wires in the cable and a pair is two eight wire cables. A regular pair has eight wires with pos. and neg. at each end, thus four for pos. and four for neg. Shotgun wire for 8tc has the same eight wires with only one connector at each end or four cables with eight wires each. Thus eight wires for pos and eight for neg. Oh and biwire generally has two connectors at amp end and four at speaker end.

The first time I heard the term "shotgun" was in the early 80's. It was used by MIT to describe a double run of 750 speaker wire.

I believe the term 'shotgun' refers to the cross-section resembling a 'double barrel shotgun.' That means two separate runs; one end of both cables terminate to a single point(amp end), the other terminated to connect in common bi-wire configuration.

Actually, I realize now that what I have described above is an external bi-wire configuration. True shotgun would be as mentioned by Jig: two separate cables joined to single pairs of terminations at BOTH ends.

This just keeps getting better, doesn't it?