/zif'euh soor"euhn/ , adj.
1. belonging or pertaining to the order Xiphosura, comprising the horseshoe crabs.
n.
2. an arthropod of the order Xiphosura; a horseshoe crab.
[ 1830-40; Xiphosur ( a ) order name (irreg. xíphos sword + -oura, neut. pl. of - ouros -tailed, deriv. of ourá tail) + -AN ]