A portmanteau of ass and platter, splatters are any pants or shorts worn lower than the waist that highlight the accessibility of the butt, presumably as an advertisement of one's eagerness for anal sex. Likely a carryover from the prison trend to announce homosexuality by wearing the pants low.
"Fool's wearin splatters and he ain't even gay!"
"What's with all these punks wearing splatters? You'd think it was Happy Hour at a gay bar."