1. One who acts; a person whose conduct is in question.
2. Archaic. A male plaintiff.
3. Hist. An advocate or pleader; one who acted for another in legal matters. Cf. REUS(1).
4. Roman law. (ital.) A person who sues; a claimant. — Also termed (in sense 4) petitor. Pl. (in sense 4) actores.