What is a slapper?

Now this Is a challenge. How do I put this in a politically correct way?
Slapper, in my understanding, is a slang term for a girl, or woman who is reputed to be 'of loose morals'. Usually, it's used as an insult.
I wouldn't recommend calling a girl a slapper, to her face, unless you wanted your face slapped, at the very least.
It's probably best used as a term of derision, when describing an unpopular girl, down the pub, when you're having a few lagers with your mates.
All nice and PC.

its slang for a woman who is easy to lay and if you dont understand lay thats to shag.

Well, I don't know if this is what you meant, but in the back country of USA a knee slapper is a story or a joke that makes you laugh so hard you slap your knees.

Slapper Means:A hitter who slaps (usually another person) with an open hand.
see this "someone slapped me on the back and I turned to see who the slapper was"
and also have a meaning like this: [Brit, offensive] (informal) a promiscuous woman.
aqs

a loose woman is called a slapper in the uk