So called "billet" aluminium is used in all sorts of applications, from screws to complex motor parts like intakes, throttle-bodies, wheels and valve covers. I never knew what billet meant but I assumed it was some sort of process or treatment applied to the metal, maybe like galvanizing or chroming or something.
So the Dictionary defines billet as a noun, "somewhere to lodge troops" [LINK].
It turns out that a billet is also a SHAPE of metal, like an ingot [LINK]. I suppose it’s like a measure or unit of trade. A part made from billet aluminium in this context it means the part was machined from a single piece of metal. It’s the most expensive way to form a part (vs forging for example).
You learn something new most days.