noun

1. Christianity any of certain rites instituted by Jesus and believed to be means of grace: baptism, confirmation, the Eucharist, penance, holy orders, matrimony, and Anointing of the Sick are the seven recognized by the Roman Catholic and Eastern Orthodox churches; Protestants generally recognize only baptism and the Lord's Supper (the Eucharist)
2. the Eucharist, or Holy Communion; also, the consecrated bread and wine, or sometimes the bread alone, used in the Eucharist
3. something regarded as having a sacred character or mysterious meaning
4. Archaic
   1. a symbol or token
   2. a solemn oath or pledge

Etymology: ME < OFr sacrement < LL(Ec) sacramentum, the gospel, a secret, sacrament (used as transl. of Gr mystērion) < L, an oath of allegiance, orig., sum deposited by the two parties to a suit < sacrare, to consecrate < sacer, sacred