What is wrong with my brother?

Okay. So I have a LOT of run-ins with my brother which leaves me confused and angry every single time.

So today, he was telling me how this one person he knows is an "escort". So I was thinking of one of those police escorts who escort people to events etc. And before I could even put together a sentence to answer him, he goes, "You don't know what an escort is?" So I was like, "Um.. like one of those police escorts that take you places?" And he was suddenly really worked up about it and was like, "Wow, you retard. It's job-related. Look it up." And I was like "Yeah... well, the only type of escort is the kind that protects you while you travel". And he started calling me names like "idiot" and "retard" and told me it's like common sense to know. He told me afterwards that it was a woman who accompanies a man, usually in a sexual manner, like a prostitute. I was surprised, because I had never known but my brother treated me as if I should have known that word. He even said "even a 6th grader knows".

So I was trying to tell him how not everyone knows everything and it's fine not to know certain things (especially stuff like knowing what an escort is) and he just blew up saying stuff like I don't know because I "don't know anything" and he got really mad and told me to shut up because I don't know anything.

What is wrong with my brother??? Can ADD or ADHD cause this kind of behavior? What can I do about this?