A shortened derogatory noun or adjective used by Mexicans. As an adjective, it signifies mocking ignorance. It comes from "Buey" (meaning an ox with its genitalia cut off). The meaning is strong enough, the use of this word may be offensive unless you use it to playfully name a close friend.
Someone being named "wey" by a friend is playfully being called an "ox with its genitalia cut off".
Oye, wey. Pasame el libro. (Hey, buddy, pass me the book).