the classic hair style of the late 90's in which the bangs of the hair are made to stand up; which then evolved into the "blow out" which is now used by virtually all people who go clubbing
Hey wanna go play soccer? Yeah, just got my new flip up.
To have an erection and attempt to disguise it by flipping your penis upwards -- so it is held between you underwear/pants and you waistline.
My teacher asked me to stand up in class, I had a huge boner so I needed to flip up quickly before I stood.