A moped is a person you are having
fun dating, but would never want your friends or family to meet because they are
ugly or a total loser.
Like a moped your date is
fun to ride, but you would never want your friends or family to see you on it.
I've been seeing a girl for several months, but I can
never introduce her to my friends or
family because they would make
fun of me because she is a total moped.