An unforeseen source of danger; a pitfall.
An antipersonnel device deliberately hidden or disguised as a harmless object.
A practical joke by which something is made to fall upon someone entering through a door, or the like.
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.
Subsidence below ground in a mine, which can cause the ground level above to drop.