Gravity bomb

A gravity bomb is an aircraft-delivered bomb that does not contain a guidance system and hence follows a ballistic trajectory.This described all aircraft bombs until the latter half of World War II and the vast majority until the late 1980s.
Then, with the dramatically increased use of precision guided munitions, a new term was needed to separate 'smart bombs' from those that weren't. Dumb bomb was used for a time, but many in military circles felt it sounded too trite, and eventually 'gravity bomb' gained currency. Previously they were also referred to as Iron bombs.
Special types of gravity bombs include retarded gravity bombs, which use a mechanical method of creating increased drag, such as a parachute, ballute or drag-inducing petals. These deploy after the bomb is released and slow its fall, giving the aircraft time to get clear of the blast zone when bombing from low altitude.