1. a sign, token, or symbol; pledge.

2. something regarded as possessing a sacred character or mysterious significance.

3. a holy rite of passage.

4. Christianity: a visible sign of an inward grace, especially one of the solemn Christian rites considered to have been instituted by Jesus Christ to symbolise or confer grace.

5. (often initial capital letter) Also called Holy Sacrament; the Eucharist or Lord’s Supper.

Etymology: from Church Latin sacrāmentum, “vow”, from Latin sacrāre, “to consecrate”.

[Emily Balivet - Alchemical Wedding Sacred Marriage]