plain·tiff /'plān-təf/ n [Middle French plaintif, from plaintif, adj., grieving, from plaint lamentation, from Latin planctus, from plangere to strike, beat one's breast, lament]: the party who institutes a legal action or claim (as a counterclaim) see also complainant, complaint, libellant compare defendant, prosecution
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.