Green’s Dictionary of Slang

loop n.2

1. [1980s+] a fig. circle of information; usu. in phr. in the loop/out of the loop.

2. [1990s+] a pornographic film.

3. [2000s] (US black) sex involving several males and a single female.

4. (S.Afr. drugs) the plastic container for the heroin-derivative drug sugars n.

In phrases

out of the loop

[1980s+] (orig. US) not in on a secret, or unaware of what’s going on.

SE in slang uses

In phrases

go through the loops (v.)

[1940s] (Aus.) to become angry or overwrought.

on the loop

wandering around; thus take it on the loop, to leave.

put the loop on (v.) [image of a lasso]

[1920s] (US) to capture.