I've seen several references to a loop lighting pattern, often in the context of portraiture lighting.
What is meant by the term?
image (c) portraitlighting.net
It's where you have the lightsource above and slightly behind the subject so the light runs down the nose and creates a loop shaped shadow.
Personally I don't like the shadow, I either go for something more dramatic and join the nose shadow to the unlit side leaving just a triangle highlight on cheek or go for a broad lighting setup if I want a flattering well lit scheme.