a. Pertaining to a master; magisterial; authoritative; dogmatic. a. Commanded or prescribed by a magister, esp. by a doctor; hence, effectual; sovereign; as, a magistral sirup. a. Formulated extemporaneously, or for a special case; -- opposed to officinal, and said of prescriptions and medicines. n. A sovereign medicine or remedy. n. A magistral line. n. Powdered copper pyrites used in the amalgamation of ores of silver, as at the Spanish mines of Mexico and South America.