Short for Big Phyllis. It is the name of the evil twin in a set of twins. Usually if one of the twins is male and one is female, then the female one is Big Phyl, but not always.
-Bro, your sister is such a jerk, I can't believe she's your twin!
-I know man, she's definitely Big Phyl!
-I know man, she's definitely Big Phyl!
by AJBROSON October 26, 2010