Webster's Revised Unabridged Dictionary · 1913

Rubric

Rubric , noun

[Old English rubriche, Old French rubriche, French rubrique ( compare it. rubrica), from Latin rubrica red earth for coloring, red chalk, the title of a law (because written in red), from ruber red. See red.]

(Law books) That part of any work in the early manuscripts and typography which was colored red, to distinguish it from other portions.
(a)
(Law books) A titlepage, or part of it, especially that giving the date and place of printing; also, the initial letters, etc., when printed in red.
(b)
(Law books) The title of a statute; -- so called as being anciently written in red letters.
(c)
(Law books) The directions and rules for the conduct of service, formerly written or printed in red; hence, also, an ecclesiastical or episcopal injunction; -- usually in the plural. — Bell
All the clergy in England solemnly pledge themselves to observe the rubrics. — Hook
(d)
Hence, that which is established or settled, as by authority; a thing definitely settled or fixed. — Cowper
Nay, as a duty, it had no place or rubric in human conceptions before Christianity. — De Quincey

Rubric , transitive verb

To adorn ith red; to redden; to rubricate. [Rare] — Johnson

Rubric , adjective

1.
Colored in, or marked with, red; placed in rubrics.
What though my name stood rubric on the walls Or plaistered posts, with claps, in capitals? — Pope
2.
Of or pertaining to the rubric or rubrics.
Rubrical eccentricities. — C. Kingsley

Also: Rubrical