A human being shaped so perfectly that their hotness is almost painful to look at:
Boys; know you've met a ten when she tells you a joke and you accidentally spit coke in her face.
Girls; know you've met a ten when the fact that he's even speaking to you makes you wet.
Be careful! Tens know it. They have mirrors too. Their prettyness is so intense that you will forgive anything just to be around them. They are not always nice people.