Definition of: equinoctial

(ē′kwə·nok′shəl) adjective
1. Occurring at or near the time when the sun crosses the celestial equator.
2. Of or pertaining to the equinox, or equality of day and night.
3. Bot. Opening and closing at regular hours: said of certain flowers, as the four–o'clock.
4. Of or pertaining to the equator or equatorial regions.
—noun
1. Meteorol. A severe storm occurring usually at or near the equinox: also called, locally, line storm.
2. The equator. See EQUINOX. [<L aequinoctialis <aequinox EQUINOX]