tri·​lo·​bite ˈtrī-lə-ˌbīt How to pronounce trilobite (audio)
: any of numerous extinct Paleozoic marine arthropods (group Trilobita) having the segments of the body divided by furrows on the dorsal surface into three lobes

Illustration of trilobite

Illustration of trilobite
  • trilobite fossil

Example Sentences

Recent Examples on the Web That’s because, with the animals arranged in lines, their librigenal spines are typically touching those of the trilobite immediately ahead of or behind them. Gemma Tarlach, Discover Magazine, 17 Oct. 2019 Researchers worked with information from 295 trilobite fossils collected in New York state. Sam Walters, Discover Magazine, 25 July 2022 Other species, like Diploneis smithii, whose segmented shell resembles a slender trilobite, prefer saline waters. Jack Tamisiea, WIRED, 24 Sep. 2022 As a high school graduation gift, Gary A. Jennison III received a plaque containing a 400-million-year-old trilobite fossil. Globe Staff,, 13 June 2022 All that changed when Losso and her colleagues took a closer look at a 508-million-year-old trilobite fossil from the famous Burgess Shale deposit in British Columbia. Joanna Thompson, Scientific American, 3 June 2022 When it was placed on Wednesday’s House calendar, House Minority Leader Blake A. Filippi, a Block Island Republican, engaged in some tongue-in-cheek trilobite trolling. Globe Staff,, 2 May 2022 Additionally, researchers have found fossilized excrement that also contains trilobite shells, strengthening the cannibalism theory (which, while strong, is still merely a theory). Daisy Hernandez, Popular Mechanics, 13 Apr. 2022 This particular trilobite could see about 200 facets or pixels. Ashley Strickland, CNN, 13 Aug. 2020 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'trilobite.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


borrowed from German Trilobit, from New Latin trilobus "three-lobed" (borrowed from Greek trílobos, from tri- tri- + -lobos, adjective derivative of lobós lobe) + German -it -ite entry 1

Note: German Trilobit was introduced by the theologian and naturalist Johann Ernst Immanuel Walch (1725-78) in Die Naturgeschichte der Versteinerungen zur Erläuterung der Knorrischen Sammlung von Merkwürdigkeiten der Natur ("The Natural History of Fossils, as a Commentary on the Knorr Collection of the Curiosities of Nature"), 3. Theil (Nuremberg, 1771) p. 120 and following. This work, in four parts issued from 1768 to 1773, was an expanded and greatly improved edition of a publication begun by the Nuremberg engraver and fossil collector Georg Wolfgang Knorr, who had died in 1761. According to Walch, "Da man dieses Petrefact Anfangs nur Stückweise entdeckte, und nicht wusste, zu was vor einer Gattung von Körpern man dasselbe rechnen sollte, so hielte sich fast jeder Naturforscher, der dasselbe bekannt machte, für berechtiget, ihm einen eigenen Nahmen beyzulegen …[there follows a discussion of various names, as concha trílobos [latter word in Greek letters], concha triloba rugosa, pectunculites trilobus, entomolithus paradoxus, Dudley fossil, etc.]…Alle aber, zusammen genommen, sind ihm gegeben worden, entweder von seiner Gestalt und Aenlichkeit, die es mit andern Körpern hat, oder von dem vermeintlichen Original, so man, wiewohl meist ohne Grund, dafür angesehen, oder von dem Ort und Gegend, wo man dasselbe gefunden. Wir wollen ihm die allersimpelste Benennung beylegen, und es einen Trilobiten nennen" ("Since early on only fragments of the fossil had been discovered, and no one knew the category of body under which it should be considered, almost every investigator of nature who made it known felt justified in conferring on it his own name …Taken together, all these names have been given either from its shape and similarity to other bodies, or from what is regarded, usually without any basis, as the presumed prototype, or from the place where it was found. We want to confer on it the simplest name possible, and call it a trilobite"). (Walch uses Trilobit as a weak noun, with an accusative singular Trilobiten.) Walch's Naturgeschichte der Versteinerungen was translated into Dutch (3rd Part, 1773) and French (3rd Part, 1775), with the animal designated respectively as Trilobiet and Trilobite in these languages. Further details about Walch, as well as an English translation of the French version of relevant passages from Naturgeschichte der Versteinerungen, can be found in Robert Kihm and James St. John, "Walch's Trilobite Research—A Translation of His 1771 Trilobite Chapter," Fabulous Fossils—300 Years of Worldwide Research on Trilobites, edited by D.G. Mikulic, et al., New York State Museum Bulletin 507 (Albany, 2007), pp. 115-40. Note that Walch only uses Trilobit as a vernacular designation; the class name Trilobita, though attributed to Walch in taxonomic literature, does not appear in the book.

First Known Use

1832, in the meaning defined above

Time Traveler
The first known use of trilobite was in 1832

Dictionary Entries Near trilobite

Cite this Entry

“Trilobite.” Dictionary, Merriam-Webster, Accessed 20 Mar. 2023.

Kids Definition


tri·​lo·​bite ˈtrī-lə-ˌbīt How to pronounce trilobite (audio)
: any of a group of extinct invertebrate animals that lived in Paleozoic seas, have a body composed of segments and divided lengthwise along the back into three parts, and are classified as arthropods

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