South African slang phrase essentially meaning; 'so you think you're the man?'. Often used in just about any situation even if it doesn't make any sense. Important to especially pronounce the word 'boer' at the end. The longer you can hold the 'owr' sound the more street cred is given.
Skye: Check it out man 1600 points!
Brice: So you think you're a BOER!?
Skye: Whats the time?
Brice: So you think you're a boer?
Brice: So you think you're a BOoooewwRrrr!?