noun
(Christianity) A sacred act and the attendant ceremony, considered (theology) an outward sign of divine grace, instituted by Jesus Christ.
(in particular) The Eucharist.
The consecrated Eucharist (especially the bread).
(by extension) Anything regarded as possessing a sacred character or mysterious significance.
(Ancient Rome) The oath of allegiance taken by soldiers in Ancient Rome; hence, any sacred ceremony used to impress an obligation; a solemn oath-taking; an oath.
verb
(transitive) To bind by an oath.