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.
Sharp spikes, resembling ‘jacks' used to maim a horse. Robert the Bruce used them at Bannockburn, and there are references to spurs being used for this same purpose.
A four pointed metal spike that was thrown on the ground, always with one spike upright. Used against cavalry horses.
Mediterranean annual or biennial herb having pinkish to purple flowers surrounded by spine-tipped scales; naturalized in America
a device with four sharpened spikes arranged so that no matter how it lands, one of the spikes will always point upwards
a machine composed of four spikes or points arranged so that in whatever manner it is thrown on the ground, it rests on three and presents the fourth upright
an unpleasant medieval weapon
a piece of metal that, when you throw it onto the ground, always lands so that one point sticks up into the air where it can do major damage to tires and to feet wearing anything less than good work boots
Four-pointed spike device designed so that one point always faces up.
A small iron weapon. Made up of four spikes set so that however it was layed on the ground, one spike always pointed upwards. Used against horses and infantry
A caltrop (calthrop, jack rock, star nail) is a weapon made up of two (or more) sharp nails or spines arranged in such a manner that one of them always points upward from a stable base (for example, a tetrahedron). Caltrops serve to slow down the advance of horses, war elephants, and human troops. It was said to be particularly effective against the soft feet of camels.