WordNet (r) 3.0 (2006):
Xiphosurus polyphemus n 1: large marine arthropod of the Atlantic coast of North America having a domed carapace that is shaped like a horseshoe and a stiff pointed tail; a living fossil related to the wood louse [syn: horseshoe crab, king crab, Limulus polyphemus, Xiphosurus polyphemus]