A girl with a very sexy body but an unattractive face... This phrase is generally uttered by men who examine the posterior of a lady as they drive by, On the approach they say "Oooohhh" and if her face does not match the beauty of her posterior as they pass they will say "Naaaaaa", hence Una.
Used to describe a car made to sound louder and more aggresive than it actually is. Typically done by Boy racers by fitting an aftermarket exhaust system.