D defs.my
Entry 2 senses Webster, 1913

Complainant

/(kŏm*plān"ant)/ · Com·plain·ant · IPA /kəmˈpleɪnənt/
01 n. One who makes complaint.
  1. 1.
    One who makes complaint.
    “Eager complainants of the dispute.” — Collier.
  2. 2.
    One who commences a legal process by a complaint.(Law)
    “He shall forfeit one moiety to the use of the town, and the other moiety to the use of the complainant.” Statutes of Mass.