An act of fellatio given as a non-sexual reward for accomplishing a difficult task. The reason for fellatio rather than a material reward stems from the absolute truth that fellatio is awesome. It is generally reserved for monumental feats of accomplishment - ex. landing a major client account in record time, where the potential client was leaning away from ones firm.
This blowjob is non-sexual. No attraction need (or should) exist between the giver and receiver. Receipt or gift of a PBJ is not considered homosexual if given between males, but ONLY if the PBJ is given for a legitimately monumental achievement.
Jerry: I landed the VCorp account overnight - and they were even thinking of going with the other guys!
Rob: Jerry, that's amazing. We've had sales team after sales team tell us that account was impossible! And I just assigned it to you three days ago! Tell you what, meet me in my office. You've earned a Platonic Blowjob!
Alice: Tim, I can't believe you were able to complete the entire backup automation in two hours. It even tags changes and encrypts everything! Tomorrow morning, I'll see you in your cube for a PBJ.