Real Dictionary

horseshoe crab in American English
any of an order (Xiphosura, class Merostomata) of sea arthropods shaped like the base of a horse's foot and having a long, spinelike tail
noun: a large marine arthropod, Limulus polyphemus, of shallow coastal waters of eastern North America and eastern Asia, having both compound and simple eyes, book gills, a stiff tail, and a brown carapace curved like a horseshoe: a living fossil related to the

horseshoe crab in British English
noun: any marine chelicerate arthropod of the genus Limulus, of North America and Asia, having a rounded heavily armoured body with a long pointed tail: class Merostomata