"Passenger on board" or "package on board" - the standard call in by a cab driver or despatch rider to their controller to let them know that they have made a pick-up and to confirm the destination. For a despatch rider or delivery van driver this enables the controller to route them via other pickups en route. The canonical form in UK use is "<callsign>, POB <location> for <destination>", e.g. "five two, POB SE1 for EC2".
The variant GOB (goods on board) is also known. You're less likely to hear this stuff these due to the rise of GPS-based computerised despatching systems, but I feel the old craft skills should be preserved.