Broken down, "pissed-up" means
inebriated or drunk. A "slapper" is, well, a slut. Or, a woman of loose morals. So, a "
pissed up slapper" is also known as a drunken trollop or whore.
"Lets go to the bar tonight and pick up
a couple of pissed up slappers." "Check that pissed up slapper
going down on Mark
in the corner." "It's a sure thing cause she's a pissed up slapper."