An unguided bomb, also known as a free-fall bomb, gravity bomb, dumb bomb, or iron bomb, is an aircraft-dropped bomb (conventional or nuclear) that does not contain a guidance system and hence simply follows a ballistic trajectory. It includes all aircraft bombs in general service until the latter half of World War II, and the vast majority until the late 1980s, which were known simply as "bombs".
Then, with the dramatically increased use of precision-guided munitions, a retronym was needed to separate "smart bombs" from free-fall bombs. "Dumb bomb" was used for a time, but many military circles felt it sounded trite, and eventually "gravity bomb" gained popularity.
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