According to that entry, "on fleek" means "smooth, nice, sweet." However, the term really didn't pick up in popularity until this year, 2014. As most modern cultural trends go, "on fleek"'s ...

“‘on fleek’ dates back to at least 2003, when its Urban Dictionary definition was created.” At that time, it was used to describe something that was “smooth, nice, sweet. [But] in ...