Ambush:

am'-boosh ('arabh, "to set an ambush"; ma'arabh, "an ambush"): A military stratagem in which a body of men are placed in concealment to surprise an enemy unawares, or to attack a point when temporarily undefended. This stratagem was employed successfully by Joshua at Ai (Jos 8). Jeremiah calls upon the Medes to "set up a standard against the walls of Babylon, make the watch strong, set the watchmen, prepare the ambushes" (Jer 51:12).