Allocated
A bottle whose demand outpaces what a distillery can supply, so distributors ration it across retailers in limited quantities.
Allocation is a supply-chain reality, not a rating: when demand for a bottle outstrips what a distillery can currently produce, distributors divide the limited supply across retailers in small quantities rather than letting any one store stock as much as it wants.
It happens to genuinely limited, hard-to-replicate releases, but it also happens to widely-produced bourbons that have simply become more popular than the distillery anticipated -- being allocated says a bottle is hard to find, not that it is rare in the sense of a tiny production run, and not that it is objectively better than a bottle sitting unallocated on the same shelf.