A really cool and sophisticated way to say "mullet," since anything sounds more cool and sophisticated if you pronounce it as if it were French. It also allows you to encode your comment, in case you're overheard.
It has nothing to do with fucking a cow, although there may be some correlation between having a mullet and having a desire to pork the beef.
See also low-zay
"Check out that mullet!" he said, but made sure he pronounced it "moo-lay."