noun · 2 senses · updated from the 2026-07-25 local source snapshot
Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.
Sound
Pronunciation
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1
noun
Meaning 1
The spine of a sea urchin.
Definition source: English Wiktionary via Wiktextract
Topics: biology, natural-sciences, zoology
No example sentence was provided for this meaning.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
2
noun
Meaning 2
A heavily ciliated feather-like tentacle occurring in clusters on the crowns of certain tubeworms, especially those of the order Canalipalpata (fan-head worms), used for feeding and respiration.
Definition source: English Wiktionary via Wiktextract
Topics: biology, natural-sciences, zoology
No example sentence was provided for this meaning.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
History
Etymology
From Late Latin radiolus (“a fossil echinoid’s spine”), from Latin radius (“rod, staff”) (possibly ultimately from Proto-Indo-European *reh1t- (“beam, pole, post”)) + -olus (diminutive suffix) (ultimately from Proto-Indo-European *-lós). The word first appears in the works of Scottish natural historian and marine zoologist Charles Wyville Thomson (1830–1882).
Across languages
Translations
3 source translations are retained for this English entry.
Chinese Mandarin:
輻棘 /辐棘
(fújí)
— spine of a sea urchin