The word was invented by my buddy in 1989. He was making mac and cheese, but had no
butter. He spit in the mix, instead. Me and another guy were watching, and he looked up guiltily. He said, "I can't believe I did that. It's so sleazy. It's so assinine. It's... slass." We all busted up laughing. Therefore the
definition means "part sleazy, part assinine; both sleazy and assinine." The
word has since grown to mean something more along the line of "generally negative."