Lewis & Short

assertor (ads-), ōris, m. [2. assero], one who formally asserts that another is free or a slave.

  1. I. A restorer of liberty.
    1. A. Lit.: adsertores dicuntur vindices alienae libertatis, Don. ad Ter. Ad. 2, 1, 40; cf. 2. assero, I. A.: populo detrectante dominationem atque adsertores flagitante, Suet. Caes. 80: Catoni gladium adsertorem libertatis extorque, Sen. Ep. 13.
    2. B. Trop., a defender, protector, deliverer, advocate: publicus adsertor dominis suppressa levabo Pectora, Ov. R. Am. 73: senatūs adsertor, Luc. 4, 214 (qui in libertatem defendis senatum, Schol.); Mart. 1, 53, 5: adsertores Camilli, id. 1, 25; Suet. Galb. 9: dignitatis ac potentiae patriciorum, id. Tib. 2: quaestionis, he who carries an inquiry entirely through, is master of the subject, Macr. S. 7, 4.
  2. II. He who claims or declares one to be a slave (cf. 2. assero, I. B.): cum instaret adsertor puellae, Liv. 3, 46, and besides only id. 3, 47.