radiolarian

noun

ra·​di·​o·​lar·​i·​an ˌrā-dē-ō-ˈler-ē-ən 

: any of three classes (Acantharia, Polycystina, and Phaeodaria) of usually spherical chiefly planktonic marine protozoans having radiating threadlike pseudopodia and often a siliceous skeleton of spicules

radiolarian adjective

Illustration of radiolarian

Examples of radiolarian in a Sentence

Recent Examples on the Web

These include radiolarians, dinoflagellates and diatoms, as well as many varieties of insects, microscopic flowers and even lunar samples from the Apollo program. —Jeff Spry, Space.com, 9 Nov. 2025

After which radiolarians sink, producing a steady snowfall of delicate glasswork onto the ocean floor. —Literary Hub, 28 Oct. 2025

At left, a large Thalassicolanucleata radiolarian with a central capsule enclosing the nucleus. —Discover Magazine, 3 June 2015

The organic carbon decline coincided with the disappearance of more than 50 species of radiolarians, which served as a food source for numerous marine species and whose disappearance was an indicator of a major biological crisis. —Reuters, WIRED, 10 May 2001

Word History

First Known Use

1869, in the meaning defined above

Rhymes for radiolarian

• authoritarian
• communitarian
• disciplinarian
• egalitarian
• equalitarian
• humanitarian
• majoritarian
• octogenarian
• parliamentarian
• totalitarian
• utilitarian
• agrarian

Kids Definition

radiolarian

noun

ra·​di·​o·​lar·​i·​an ˌrād-ē-ō-ˈlar-ē-ən 

-ˈler-

: any of various usually ball-shaped marine protozoans that have small spines radiating from the shell and have a skeleton containing silica