protester

Etymology

From protest + -er.

noun

1. One who protests, either alone or in a public display of group feeling.
   The protesters thronged Trafalgar Square and sang anti-war songs.
   The dispatches […] also exposed the blatant discrepancy between the west's professed values and actual foreign policies. Having lectured the Arab world about democracy for years, its collusion in suppressing freedom was undeniable as protesters were met by weaponry and tear gas made in the west, employed by a military trained by westerners. 2013-06-07, Gary Younge, “Hypocrisy lies at heart of Manning prosecution”, in The Guardian Weekly, volume 188, number 26, page 18
2. (law) One who protests a bill of exchange, or note.
   The protester must also draw up an affidavit containing the literal reproduction of the bill with its acceptance, endorsements, guarantee by endorsement ("aval"), and anything else contained in the note […] 1997, Charles Evan Stewart, Transnational Contracts, volume 1, page 96