A nickname for Massachusetts. More pleasant sounding than "Mass." The second colony. Founded in 1620. Don't mess.
The chu itself it awesome. It's beautiful, and chu is a title its worthy of. People from the chu are awesome and probably have a wicked accent. All of the kids that go to college in Boston or other areas in the chu, call it the chu. It's just what you do. People who call it mass are massholes.
Chu can also refer to the people who live there. When they have said something clever and/or hilarious, it would be appropriate to call them a chu; it is a term of endearment. Everybody wants to be a chu. And if you're a chu while in the chu, you're the coolest kid around.