τρίβολος

Noun

 * 1) name of various prickly plants:
 * 2) water chestnut
 * 3) caltrop
 * 4) caltrop, a four-spiked implement thrown on the ground to lame the enemy's horses
 * 5) larger contrivance for stopping boulders thrown down a slope
 * 6) instrument hung from the walls of a fortress as a defence against battering rams
 * 7) kind of incendiary missile
 * 1) instrument hung from the walls of a fortress as a defence against battering rams
 * 2) kind of incendiary missile

Etymology 2
Borrowed from.

Noun

 * 1) threshing sledge, a board with sharp stones fixed in the bottom
 * 2) part of the bit of a bridle
 * 1) part of the bit of a bridle