A catch-phrase originating from the 60's. Describes the massive obsessing over The Beatles. This phrase is still in use now due to the fact that the beatles have a massive legion of diehard fans that dwarfs the teenie bopper following of any pop whorelet such as Britney Spears.
The biggest proactive fan of popular british band The Beatles, who only like bands and don't say negative things about other bands. Can easily leave bisexual Directioners or faggy Beliebers behind. Know what great music actually is, and for that matter have a very good taste in music. Possibly the awesomest fandoms ever to roam the Earth.
Gal1: Dude, I am starting to like The Beatle's songs.
Guy2: I think you're becoming a Beatlemaniac.
Gal1: Is that good?
Guy2: Damn right it is. *croutches* I love the Beatles, and so do you. Will you marry me?