horseshoe crab


: any of several closely related marine arthropods (order Xiphosura and class Merostomata) with a broad crescentic cephalothorax, six pairs of legs, and a spikelike tail
especially : one (Limulus polyphemus) of coastal waters from Maine to the Yucatán Peninsula

Note: The horseshoe crab is often said to have five pairs of legs since the first pair is greatly reduced in size and used mainly for feeding. All the legs of the horseshoe crab end in claws except for the last pair of legs which have leaflike expansions used mainly for pushing.

… a horseshoe crab … is a Swiss army knife of jointed limbs—for walking, swimming, grasping, shredding, and defending. Carl Zimmer
… the horseshoe crab has changed little since an ancestor was fossilized 150 million years ago … National Geographic

called also king crab

Examples of horseshoe crab in a Sentence

Recent Examples on the Web Dinosaur shrimp, also known as tadpole shrimp, are freshwater crustaceans that look like miniature horseshoe crabs. Caroline Delbert, Popular Mechanics, 7 Sep. 2023 The birds need meaningful protection of horseshoe crab eggs to be able to recover, Niles said. Patrick Whittle, Fortune, 31 July 2023 Due to the many uses for their rare blood, every year, thousands of horseshoe crabs are taken from their habitats, and (about one-third of) their blood is harvested for biomedical use. Allison Futterman, Discover Magazine, 29 June 2023 The birds’ arrival to Delaware Bay overlaps with the yearly horseshoe crab spawning. Margaret Osborne, Smithsonian Magazine, 20 June 2023 The defendants are also barred from holding horseshoe crabs in ponds before being bled — a process that critics say kills some and weakens others. Jon Hurdle, New York Times, 15 June 2023 As a species, the horseshoe crab is more than 425 million years old. Mark Jenkins, Washington Post, 12 May 2023 Among a bonanza of fossils, the married duo has cataloged 170 marine species, including glass sponges, crustaceans called horseshoe crab shrimp, and a six-legged arthropod that may have given rise to insects. Byscience News Staff,, 4 May 2023 The decor is a pitch-perfect blend of nautical, rustic, and modern, with brick and old woodwork, vintage oil paintings and a neon horseshoe crab sign, mismatched china and chairs, and different spaces to suit different moods. Globe Staff,, 2 May 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'horseshoe crab.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1797, in the meaning defined above

Time Traveler
The first known use of horseshoe crab was in 1797

Dictionary Entries Near horseshoe crab

Cite this Entry

“Horseshoe crab.” Dictionary, Merriam-Webster, Accessed 1 Oct. 2023.

Kids Definition

horseshoe crab

: any of several closely related arthropods that have a broad crescent-shaped united head and thorax and a tail resembling a spike

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