What does caltrop mean?
A caltrop is a small, typically metal device with four sharp spikes radiating from a central point, engineered so that whichever way it falls, one spike invariably points upward. Scattered across roads, fords, and fields since antiquity, caltrops have been used to wound horses, lamed infantry, and — in modern times — puncture vehicle tyres, making them a classic example of a cheap, passive weapon that denies ground to an enemy. The name also belongs to certain spiny-fruited plants, notably Tribulus terrestris, whose burrs closely resemble the iron original and are equally unpleasant to step on. The word comes through Old French and Latin roots meaning 'heel-trap', reflecting its ancient association with hobbling foot soldiers and cavalry. Today 'caltrop' survives mainly in military history, archaeology, and accounts of roadside sabotage, retaining a distinctly sinister edge as shorthand for an unglamorous but effective instrument of delay and injury.
A small spiked metal device with four points arranged so one always faces upward when lying on the ground, scattered as an obstacle against men, horses, or vehicles.
"Archaeologists recovered rusted caltrops from the site of the medieval siege."
A spiny plant, especially Tribulus terrestris, whose hard prickly fruit resembles the military caltrop.
"The paddock was overrun with caltrop, and the cattle avoided grazing there."
The plural is standard in both senses; the device is almost always discussed in the plural, since it is effective only when many are scattered together.
"The defenders poured baskets of caltrops down onto the roadway below the walls."
A caltrop needs no mechanism and no maintenance — just four spikes welded together so that no matter how it lands, one point always aims straight up at whatever steps on it.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of caltrop
Caltrop derives from the Old English 'calcatrippe', borrowed from medieval Latin 'calcatrippa', a compound of Latin 'calx' (heel) and a Germanic element related to modern 'trap'. The literal sense is thus 'heel-trap', a fitting name for a device designed to cripple the feet and hooves of advancing troops. The same Latin root 'calx' also gives English words such as 'recalcitrant' (literally 'kicking back with the heel') and anatomical terms like 'calcaneal', relating to the heel bone.
How caltrop is actually used
Primarily a technical or historical term, encountered in military history writing and discussions of improvised anti-vehicle devices; the botanical sense appears mostly in regional or agricultural contexts. The word carries a connotation of nastiness and underhanded tactics, since caltrops injure indiscriminately rather than by direct combat.