Was a singing group that didn't sing, but lipsynched.
Now, it can be an insult to someone's singing abilities, or
if something is called "milli vanilli" its reffered to as fake.
Ex. Ashlee: omg jojo is such a good singer!!
Jason: pft. she's no mariah carey.
Mark: she's not even milli vanilli
Ex.2 Omg her louis vuitton bag is so milli vanilli