land mines

A land mine is an explosive device, concealed under or on the ground and designed to destroy or disable enemy targets as they pass over or near the device. Such devices are typically detonated automatically by way of pressure from the target stepping or driving on it, though other detonation mechanisms may be possible.^[1] The device may cause damage either by a direct blast or by fragments that are thrown by the blast.

來源：http://en.wikipedia.org/wiki/Land_mine