Meaning

noun an authoritative rule of conduct or procedure

noun an explanation or definition of an obscure word in a text

noun directions for the conduct of Christian church services (often printed in red in a prayer book)

originFrom Middle English rubriche, rubrike, from Old French rubrique, from Latin rūbrīca (“red ochre”), the substance used to make red letters, from ruber (“red”), from Proto-Indo-European *h₁rewdʰ-.

Etymology from Wiktionary, CC BY-SA 3.0