Noah Webster's New International Dictionary of the English Language

1. (a.) Relating to external rite or ritual; as, a ceremonial occasion; according to the forms of established rites.

2. (a.) Observant of forms; ceremonious. [In this sense ceremonious is now preferred.]

3. (n.) A system of rules and ceremonies, enjoined by law, or established by custom, in religious worship, social intercourse, or the courts of princes; outward form.

4. (n.) The order for rites and forms in the Roman Catholic church, or the book containing the rules prescribed to be observed on solemn occasions.