equinoctial

American  

[ee-kwuh-nok-shuhl, ek-wuh-] / ˌi kwəˈnɒk ʃəl, ˌɛk wə- /

adjective

1. pertaining to an equinox or the equinoxes, or to the equality of day and night.

2. pertaining to the celestial equator.

3. occurring at or about the time of an equinox.

4. Botany. (of a flower) opening regularly at a certain hour.

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noun

1. celestial equator.

2. equinoctial storm.

equinoctial British  

/ ˌiːkwɪˈnɒkʃəl /

adjective

1. relating to or occurring at either or both equinoxes

2. (of a plant) having flowers that open and close at specific regular times

3. astronomy of or relating to the celestial equator

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noun

1. a storm or gale at or near an equinox

2. another name for celestial equator

equinoctial Scientific  

/ ē′kwə-nŏk′shəl,ĕk′wə- /

1. Relating to an equinox.

2. Relating to the celestial equator.

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1. See celestial equator

Other Word Forms

• interequinoctial
  adjective

Etymology

Origin of equinoctial

1350–1400; Middle English < Latin aequinoctiālis pertaining to the equinox. See equinox, -al ¹

Explanation

If something happens right around the time of an equinox — the two days each year when day and night are of equal length — you can describe it as equinoctial. If your birthday falls on the spring equinox, you can call it equinoctial, and you could also call the fall hurricanes in your coastal town equinoctial storms. In either case, the thing that makes something equinoctial is its proximity to the dates in the spring and fall when the Earth isn't tipped toward or away from the sun but is positioned so the equator lines up with it. The Latin roots are aequus, "equal," and nox, "night."

Example Sentences

Crokes Cross shares the record for longest-priced winner with Blowers, which won at the same price at Exeter in December, beating the previous record of 250-1, set at Kelso by Equinoctial in1990.

From BBC • Apr. 3, 2026

The previous record was held by Equinoctial, who triumphed at Kelso in November 1990 at 250-1.

From BBC • Dec. 18, 2025

He divided them into three classes: Meteoric, Tropical, and Equinoctial flowers.

From Old-Time Gardens Newly Set Forth by Earle, Alice Morse

On the Cretan coins was the Equinoctial Bull; and he also appeared on those of the Mamertins and of Athens.

From Morals and Dogma of the Ancient and Accepted Scottish Rite of Freemasonry by Pike, Albert

Equinoctial gales again swept the sea; and thus the wholesome exercise of swimming, so useful in restoring equilibrium to the faculties and calming the mind, was forbidden.

From My Recollections of Lord Byron by Jerningham, Hubert E. H. (Hubert Edward Henry), Sir