Eclipse/ɪˈklɪps/ Definition 1 of 3Pro Tip 1/3Astronomical Event Use 'eclipse' when talking about the moon or sun being covered. The eclipse caused darkness in the middle of the day. Pro Tip 2/3Rare Occurrence 'Eclipse' refers to a rare and fascinating celestial event, often anticipated with excitement. We traveled far to observe the solar eclipse. Pro Tip 3/3Visibility Varies An eclipse's visibility depends on geography; not everyone sees it. Unfortunately, the lunar eclipse wasn't visible from our location.