An underage teens mom who lets his or her friends get drunk and do drugs in her house, sometimes engaging in drinking and drugging with the kids. The "cool" mom. Not to be confused with a MILF, although sometimes can be.
Jane: Mary, this is my mom.
Mary: Hey mamadukes, where's the booze.
Mamadukes: In the basement with the crack and PCP..Just don't tell your parents.
Mary and Jane: XD