Box
"Box" is the radio call telling a driver to pit at the end of the current lap.
Also called box box box
From the German Boxenstopp — the pit garages are the boxes. It is repeated because radio over a screaming engine is unreliable, and mishearing it costs a race either way.
Teams sometimes use it as a decoy on an open channel, calling a driver in and leaving them out to bait a rival into reacting.