caltrop

Meanings

1. A metal object, usually small, with spikes arranged so that, when thrown onto the ground, one always faces up as a threat to pedestrians, horses, and vehicles (also used as a heraldic charge).
2. The starthistle, Centaurea calcitrapa, a plant with sharp thorns.
3. Any of a number of flowering plants in the family Zygophyllaceae, including several members of the genus Kallstroemia and the species Tribulus terrestris, native to warm temperate and tropical regions.

Etymology

From Middle English calketrappe, from Old English calcatrippe, from Medieval Latin calcatrippa (“thistle”), from Latin calx or calcare (“to tread”) + trappa (“trap”).