n (astronomy) The point where the orbit of a planet, as viewed from the Sun, intersects the ecliptic. The ascending and descending nodes refer respectively to the points where the planet moves from S to N and N to S. The respective symbols are ☊ and ☋.
n (medicine) A hard concretion or incrustation which forms upon bones attacked with rheumatism, gout, or syphilis; sometimes also, a swelling in the neighborhood of a joint.
n (music) One of the fixed points of a sonorous string, when it vibrates by aliquot parts, and produces the harmonic tones; nodal line or point.
n (rare) The knot, intrigue, or plot of a piece.
n (context|technical) A hole in the gnomon of a sundial, through which passes the ray of light which marks the hour of the day, the parallels of the Sun's declination, his place in the ecliptic, etc.