This described all aircraft bombs in general service 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 military circles felt it sounded too trite, and eventually 'gravity bomb' gained currency. Previously, they were also referred to as iron bombs.
A special type of gravity bomb is the retarded gravity bomb, which uses a mechanical method of creating increased drag, such as a parachute, ballute, or drag-inducing petals. These deploy after the ordnance is released, slowing its fall and abbreviating its forward trajectory, giving the aircraft time to get clear of the blast zone when bombing from low altitudes or with nuclear ordnance.