(pharmacology) a book containing a compilation of pharmaceutical products with their formulas and methods of preparation; "postexposure prophylaxis is an integral part of the pharmacopeia in preventing severe disease after acute infections"
based on or subject to individual discretion or preference or sometimes impulse or caprice; "an arbitrary decision"; "the arbitrary rule of a dictator"; "an arbitrary penalty"; "of arbitrary size and shape"; "an arbitrary choice"; "arbitrary division of the group into halves"