Pronounced "bee tee DUBS", a spoken form of the acronym btw which stands for "by the way."
It makes little sense, as the term itself has as many syllables as the phrase it's meant to abbreviate. Accordingly, it's degenerated into a cutesy term used mostly by girls. It has also been used in the gay community as a candid way of letting others know you are a bottom.
Jason: That's a very cute outfit you're wearing, btdubs.
Bruce: Great, I'm a top. See you at my place at 9?
Joe: Yo Mike- you got a pen I can borrow?
Mike: Nah man, but why don't you ask Tracy. That hoe is PENRICH.
Joe: Her pens are probably filthy. I hear she gets em workin the corner every night in the red light district.