Someone who looks up "retard" in the Urban Dictionary, only to find that they should know what a retard is, and they don't.
Don't know what a retard is? Then you are one. Simple.
A person who looks up retard in the dictionary not knowing what it is.
If you look up something you are MEANT to know, and don't know it, you are a retard
Me
Wow look how retarded he is he got a 27/8,000,000 on the test.
A person that is so stupid that they are on the same I.Q. level as a sped
"oh my god, you're such a fucking retard"