1. Relating to an equinox (when the lengths of night and day are equal)
   "The equinoctial storms often occur around the time of the spring and fall equinoxes"
    
2. Relating to the vicinity of the equator
   "The equinoctial regions experience relatively constant day lengths throughout the year"

1. The great circle on the celestial sphere midway between the celestial poles
   "The equinoctial circle is used as a reference for measuring celestial coordinates";
   - celestial equator, equinoctial circle, equinoctial line

Derived forms: equinoctials

Type of: great circle

Encyclopedia: Equinoctial