Meaning

noun the straight line configuration of 3 celestial bodies (as the sun and earth and moon) in a gravitational system

originFrom Late Latin sȳzygia (“a conjunction”), from Ancient Greek συζυγία (suzugía, “a union, a yoke, a pair”). This word was recognized as English in 1847 (in its astronomical meaning).

Etymology from Wiktionary, CC BY-SA 3.0