mag·is·tral 
(măjĭ-strəl)
(măjĭ-strəl)adj.
1. Of or relating to a magistrate; magisterial.
2. Prepared as specified by a physician's prescription. Used of medicine.
3. Principal; main: the magistral line of fortifications.
[Late Latin magistrālis, belonging to a master, from Latin magister, magistr-, former chief officer of a college; see meg- in the Appendix of Indo-European roots.]