Short for *commercial off-the-shelf*, an adjective that describes software or hardware products that are ready-made and available for sale to the general public. For example, Microsoft Office is a COTS product that is a packaged software solution for businesses. COTS products are designed to be implemented easily into existing systems without the need for customization.

http://www.webopedia.com/TERM/C/COTS.html

off the shelf item -cCommercially produced, ready made, standardized, and regularly available equipment, goods, parts, software, etc.

http://www.businessdictionary.com/definition/off-the-shelf-i...

The definition of off-the-shelf is something that is in stock and not customized.
http://www.yourdictionary.com/off-the-shelf

Commercial-off-the-shelf (COTS) software and services are built and delivered usually from a third party vendor. COTS can be purchased, leased or even licensed to the general public.
http://en.wikipedia.org/wiki/Commercial_off-the-shelf