British Slang
In normal
society, slag is a derogatory term meaning frequently promiscuous and immoral. Typically a woman described as a slag might also be described as
easy or cheap. It is strongly associated with women who, without consideration of there partner of the moment, seeks sexual gratification. The word is very offensive to women.
In the swinging scene, where there are tiers of sexuality, the word is associated with high sexual
status, and is therefore coveted. Remarkably, as it is so offensive in everyday use, it is often used during intercourse as a compliment in recognition of sexual
skill.