Protein arrays (also biochip, proteinchip) are measurement devices used in biomedical applications to determine the presence and/or amount (referred to as quantitation) of proteins in biological samples, e.g. blood. Usually a multitude of different capture agents, most frequently monoclonal antibodies, are deposited on a chip surface (glass or silicon) in a miniature array. This format is often also referred to as a microarray (a more general term for chip based biological measurement devices).
A related technology, albeit for the measurement of RNA and DNA are DNA microarrays.
proteinarray.org is a Wiki dedicated to protein array technology.