Doy or doi is the pop culture insult that says, "no kidding!" or "that was pretty self-evident, and you're stupid." It is the same derogatory meaning as duh or doh.
How 'Doy' Is Used Online
You would say "doy" in any text chat or in-person conversation when the other person exclaims something that is painfully obvious to the rest of the group.
Examples of 'Doy'
Greg: Hey, this ice is cold.
Susan: Doy, genius!
Tuan: Are you at home right now?
Suresh: Doy! Can't you hear my parents yelling in the background?
Kandace: Do you have a cat?
Alvin: Doy! Can't you see all the fur stuck to my coat?
Origin of the Doy/Doi/Duh Expression
While the origin of doy/doi/duh is up for debate, some people say that it is an English variation of the Russian 'да' word, which means yes. According to other pop culture historians, doy/doi/duh was popularized by the comic book Archie.
Doy, like most cultural curiosities and memes of the web, has become part of daily English communications.