sacrament

A sacred act or ceremony in Christianity. In Catholic theology, a sacrament is defined as "an outward sign instituted by Christ to give grace."

(in particular) The Eucharist.

The consecrated Eucharist (especially the bread).

A thing which is regarded as possessing a sacred character or mysterious significance.

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.