CALTROP (from the Mid. Eng. calketrappe, probably de rived from the Lat. calx, a heel, and trappa, late Lat. for a snare), an iron ball, used as an obstacle against cavalry, with four spikes so arranged that, however placed in or on the ground, one spike always points upwards. It is also the botanical name for several species of thistles.
'It has been variously ascribed to Virgil, Ovid, Lucan, Statius, and Saleius Bassus.
a town of eastern France, in the department of Rhone, 21m. N. by E. of Lyons. Pop. (i931), 15,018. It makes velvet, combs and pins and has copper and bronze foundries and nursery-gardens.