sacrament

Short definition from Wiktionary

Noun

1. 1
   A sacred act and the attendant ceremony, considered (theology) an outward sign of divine grace, instituted by Jesus Christ.
2. 2
   The Eucharist.
3. 3
   The consecrated Eucharist (especially the bread).
4. 4
   Anything regarded as possessing a sacred character or mysterious significance.
5. 5
   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

1. 1
   To bind by an oath.