n. (also caltrap) 1 hist. a four-spiked iron ball thrown on the ground to impede cavalry horses. 2 Heraldry a representation of this. 3 any creeping plant of the genus Tribulus, with woody carpels usu. having hard spines.
[ (sense 3) OE calcatrippe f. med.L calcatrippa: (senses 1-2) ME f. OF chauchetrape f. chauchier tread, trappe trap: ult. the same word ]