Webster's 1828 Dictionary
CALTROP
n. 1. A kind of thistle, the Latin tribulus, with a roundish prickly pericarp; on one side, gibbous, often armed with three or four daggers; on the other side, angular, converging with transverse cells. It grows in France, Italy and Spain, among corn, and is very troublesome, as the prickles run into the feet of cattle.
2. In military affairs, an instrument with four iron points, disposed in a triangular form, so that three of them being on the ground, the other points upward. These are scattered on the ground where an enemys cavalry are to pass, to impede their progress by endangering the horses feet.
Webster's 1913 Dictionary
CALTROP; CALTRAP
Cal "trop, Cal "trap, n. Etym: [OE. calketrappe, calletrappe, caltor (in both senses ), fr. AS. collræppe, calcetreppe, sort of thistle; cf. F. chaussetrape star thistle, trap, It. calcatreppo, calcatreppolo, star thistle. Perh. from L. calx heel + the same word as E. trap. See 1st Trap. ]
1. (Bot. )
Defn: 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.
2. (Mil. )
Defn: 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.
New American Oxford Dictionary
caltrop
cal trop |ˈkaltrəp, ˈkôl -ˈkæltrəp | ▶noun 1 a spiked metal device thrown on the ground to impede wheeled vehicles or (formerly ) cavalry horses. 2 a creeping plant with woody carpels that typically have hard spines and resemble military caltrops. [Genus Tribulus, family Zygophyllaceae. ] 3 (also water caltrop ) another term for water chestnut ( sense 3 ). ORIGIN Old English calcatrippe, denoting any plant that tended to catch the feet, from medieval Latin calcatrippa, from calx ‘heel ’ or calcare ‘to tread ’ + a word related to trap 1. Sense 1 was probably adopted from French.
Oxford Dictionary
caltrop
caltrop |ˈkaltrəp | ▶noun 1 a spiked metal device thrown on the ground to impede wheeled vehicles or (formerly ) cavalry horses. 2 a creeping plant with woody carpels that typically have hard spines and resemble military caltrops. ●Genus Tribulus, family Zygophyllaceae. 3 (also water caltrop ) another term for water chestnut ( sense 3 ). ORIGIN Old English calcatrippe, denoting any plant which tended to catch the feet, from medieval Latin calcatrippa, from calx ‘heel ’ or calcare ‘to tread ’ + a word related to trap 1. Sense 1 was probably adopted from French.
The Wordsmith Dictionary