1a spiked metal device thrown on the ground to impede wheeled vehicles or (formerly) cavalry horses:militant demonstrators threw a box of caltrops across the highway
2a creeping plant with woody carpels that typically have hard spines and resemble military caltrops.
Old Englishcalcatrippe, denoting any plant which tended to catch the feet, from medieval Latin calcatrippa, from calx 'heel' or calcare 'to tread' + a word related to trap1. sense 1 was probably adopted from French
caltrop in other Oxford dictionaries
Definition of caltrop in the US English dictionary
