sacrament

n. 1 symbolic christian ceremony, e.g. Baptism and eucharist. 2 (also blessed or holy sacrament) (prec. By the) eucharist. 3 sacred thing.  sacramental adj. [latin: related to *sacred]

n. The oath of allegiance taken by Roman soldiers; hence, a sacred ceremony used to impress an obligation; a solemn oath-taking; an oath.