The girl you date for a few weeks after you break up with your dream girl. She's usually the one you date if you can't get the one you want. She's never the first choice.
A crasher girl is someone who dress like a boy (opposite of femboy) often has low voices and masculine, often acts like a man. (Basically a tomboy if you put it in that way).
A girlcrush is when a girl admires another girl. It is NOT a sexual attraction. It means you want to BE the person you have a girlcrush on, or simply you just want to be there best friend. You pretty much just think they're awesome.
Rachel: I have a girlcrush on Ellen. She's so hot why can't i be her.