A product that is commercially available.
Sources:
NIST SP 800-152
under COTS product
Software and hardware that already exists and is available from commercial sources. It is also referred to as off-the-shelf.
Sources:
NISTIR 7622
under Commercial off-the-shelf
Hardware and software IT products that are ready-made and available for purchase by the general public.
Sources:
NISTIR 7711
under Commercial-Off-The-Shelf