IMMER'SION, noun The act of putting into a fluid below the surface; the act of plunging into a fluid till covered. 1. The state of sinking into a fluid. 2. The state of being overwhelmed or deeply engaged; as an immersion in the affairs of life. 3. In astronomy, the act of entering into the light of the sun, as a star, so as to be enveloped and invisible to the eye; or the state of being so enveloped. Also, the entrance of the moon into the shadow of the earth, at the commencement of an eclipse; or the state of being enveloped in the shadow. It is opposed to emersion. The time when a star or planet is so near the sun as to be invisible; also, the moment when the moon begins to be darkened, and to enter the shadow of the earth.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI