1. An instrument with four iron spikes disposed in a triangular form, so that when three are on the ground the other points upward, sometimes used to impede the progress of an enemy's cavalry, by endangering the horses feet; a kind of thistle.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• xaltrop,
• valtrop,
• faltrop,
• daltrop,
• czltrop,
• csltrop,
• cwltrop,
• cqltrop,
• caktrop,
• captrop,
• kaltrop,
• calotyope,
• calterap,
• cantrp,
• cantrapp,
• cantriop,
• canntrip,
• Cantryp,
• ulltron,
• teiltree

• caldron,
• caulder,
• callitris,
• cauldron,
• callithrix.

The adjective form of the word "caltrop" is "caltropian".

The plural of the "caltrop" can be the "caltrops".

The singular of the "caltrop" can be the "caltrop".