It's the short version of 'are you'.
Chris: R u going out tonight?
Amy: No.
this is the american alphabet for my 3 yr olds
The word a b c d e f g h i j k l m n o p q r s t u v w x y z means hello
It is a L I F E S T Y L E
A: So, what do you do for a living?
Me, an Intellectual: T U R B O I N T
a spaced-out version of bruh. used to indicate an absolute bruh momment
one guy: hey i got an a+
me: b r u h everyone knows that