term:

Prior Art

prior art n

: the processes, devices, and modes of achieving the end of an alleged invention that were known or knowable by due diligence before and at the date of the invention
;also
: the knowledge or description of such processes, devices, or modes used chiefly in patent law

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.