A heterosexual male who spends much of his social time with lesbians. Derived from the words lesbian and pervert, thought to stem from the notion that the man is likely to harbour perverted intentions towards his lesbian friends, possibly secretly and despite outward protestations.
A male fag hag
H: I'm heading to lesbian bar Candy Bar in Soho to dance all day at Gay Pride.
S: Your a man and straight?
H: But I'm a massive lesbert and love watching the girls make out...