magistral (adj.)

1570s, "forming part of the accepted course of teaching," a sense now obsolete, from Latin magistralis "of a master," from magister "chief, director" (see master (n.)). Meaning "authoritative; of, pertaining to, or befitting a master" is from c. 1600. In pharmacy, of a remedy, etc., "devised by a physician for a particular case, prepared for the occasion" (c. 1600).