- Obscurity, decline, downfall
- A seasonal state of plumage in some birds, notably ducks, adopted temporarily after the breeding season and characterised by a dull and scruffy appearance.
- (astronomy) An alignment of astronomical objects in which a planetary object (for example, the Moon) comes between the Sun and another planetary object (for example, the Earth), resulting in a shadow being cast by the middle planetary object onto the other planetary object.
- (Irish grammar) To undergo eclipsis.
- (transitive) To overshadow; to be better or more noticeable than.
"The student’s skills soon eclipsed those of his teacher."
- (transitive) Of astronomical bodies, to cause an eclipse.
"The Moon eclipsed the Sun."