The abbreviation some people use to shorten the name of the popular smoothie place Booster Juice, especially in form of texting. These people probably just want everyone to think they are getting a blowjob, when in fact they are sipping on a smooth fruity beverage. Jokes on you!
PS. Not something to beat your boyfriend for.
Mary: so wat r u up 2?
Bill: txting u!
Mary: wat else?
Bill: having a bj!
Mary: and texting me? thats talent...
Mary later cries herself to sleep because she thought the object of her affection, Bill, was getting a blowjob from another girl. In actuality, Bill was merely sipping on some tasty Booster Juice alone.