from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun Any of various plants bearing small spiny fruits, especially of the genera Tribulus and Kallstroemia.
  • noun A metal device with four projecting spikes so arranged that when three of the spikes are on the ground, the fourth points upward, used as a hazard to pneumatic tires or to the hooves of horses.

from The Century Dictionary.

  • To entangle with caltrops.
  • noun In the nomenclature of the spicular elements of sponges, a tetraxial spicule having the form of a caltrop, with four equal simple smooth arms radiating from a central point.
  • noun plural In entomology, the short, sharp, curved spines which occur in scattered groups in the integument of certain lepidopterous larvæ of the family Limacodidæ, and which are responsible for the urticating effect produced on the human skin by these larvæ.
  • noun Formerly, a military instrument with four iron points disposed in such a manner that, three of them being on the ground, the fourth pointed upward. Caltrops were scattered on the ground where an enemy's cavalry were to pass, to impede their progress by wounding the horses' feet.
  • noun plural Broken pottery or coarse pots of easily broken earthenware, or other things adapted to wound horses' feet, used in place of caltrops proper.
  • noun In botany, a name of several plants.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Bot.) A genus of herbaceous plants (Tribulus) of the order Zygophylleæ, having a hard several-celled fruit, armed with stout spines, and resembling the military instrument of the same name. The species grow in warm countries, and are often very annoying to cattle.
  • noun (Mil.) An instrument with four iron points, so disposed that, any three of them being on the ground, the other projects upward. They are scattered on the ground where an enemy's cavalry are to pass, to impede their progress by endangering the horses' feet.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun weaponry A small, metal object with spikes arranged so that, when thrown onto the ground, one always faces up as a threat to passers-by.
  • noun colloquial The starthistle, Centaurea calcitrapa, a plant with sharp thorns.
  • noun A flowering plant, Tribulus terrestris, in the family Zygophyllaceae, native to warm temperate and tropical regions of the Old World.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a plant of the genus Trapa bearing spiny four-pronged edible nutlike fruits
  • noun Mediterranean annual or biennial herb having pinkish to purple flowers surrounded by spine-tipped scales; naturalized in America
  • noun tropical annual procumbent poisonous subshrub having fruit that splits into five spiny nutlets; serious pasture weed


from The American Heritage® Dictionary of the English Language, 4th Edition

[Middle English calketrappe, from Norman French and from Old English calcatrippe, thistle, both from Medieval Latin calcatrippa, thistle : possibly from Latin calcāre, to tread on; see calque + trappa, trap (of Germanic origin).]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From the Latin calcitrapa ("thistle").


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  • "The 37 caltrops found in the garage of the home, nail-like devices used to stop traffic or puncture wheels, are also not evidence or conspiracy to commit a riot, Nestor says. 'Did they have some devices to try to block traffic? Maybe so,' Nestor asserts. 'But does that mean they should be arrested on conspiracy charges? Not at all. This was intended to halt the protests.'�?

    - Molly Priesmeyer, 'Police seize ‘propaganda literature,’ staples, curtain rods, and caltrops from raided home on 17th Avenue' in Minnesota Independent, 30 August 2008.

    September 25, 2008