A small, metal object with spikes arranged so that, when thrown onto the ground, one always faces up as a threat to pedestrians, horses, and vehicles.
The starthistle, Centaurea calcitrapa, a plant with sharp thorns.
The same object represented as a heraldic charge.
Any of a number of flowering plants in the family Zygophyllaceae, including several members of the genus Kallstroemia and the species Tribulus terrestris, native to warm temperate and tropical regions.
Subsidence below ground in a mine, which can cause the ground level above to drop.
A potential, unsuspected, hidden problem, hazard, or danger that is easily encountered but not immediately obvious.
A type of trap consisting of a concealed pit in the ground, which the victim is supposed to fall into and not be able to get out from.
An antipattern.