A "Double Noose" is a knot that has two loops that may be tightened or loosened.
It is rarely seen due to the complexity that would be required to tie it, let alone draw it.

Another form of the double noose is a "Handcuff knot".

In the context of this tag, it should be used to describe a hangman's noose designed for two condemned to be hanged simultaneously, against one another (either back to back, face to face, or "spooning", from a single attachment point on a gallows or other fixture.