Magistral meaning : A sovereign medicine or remedy. A magistral line. Powdered copper pyrites used in the amalgamation of ores of silver, as at the Spanish mines of Mexico and South America. Pertaining to or befitting a master; authoritative. (pharmaceutical effect) Sovereign (of a remedy); extremely effective. Formulated extemporaneously, or for a special case; opposed to officinal, and said of prescriptions and medicines.