two bodies sharing an orbit like flatmates who never quite bump into each other.
means a celestial object that shares essentially the same orbital path around a parent body as another object, without merging or colliding.
from from co- (together) plus orbital, coined as astronomers found moons and asteroids that don't collide with planets or each other despite sharing an orbit, thanks to gravitational resonances that keep them politely spaced.
earth and 3753 cruithne — asteroid traces a horseshoe path relative to earth, discovered 1986
janus and epimetheus — saturn's moons swap orbital radii every four years without colliding
jupiter trojans — thousands of asteroids share jupiter's orbit at l4 and l5, since 1906
telesto and calypso — tiny saturn moons riding tethys's l4 and l5 points