A bomb is an explosive device that, although not containing more energy than ordinary fuel, except in the case of a nuclear weapon, generates and releases its energy very rapidly, as an explosion, a violent, destructive shock wave. It is usually some kind of container filled with explosive material, designed to cause destruction when set off. The word comes from the Greek word βόμβος (bombos), an onomatopoetic term with approximately the same meaning as "boom" in English.

These are first and foremost weapons; the term "bomb" is not usually applied to explosive devices used for civilian purposes, such as construction or mining, although the people using the devices may or may not sometimes refer to them as bombs. Many military explosive devices are not called "bombs". The military mostly calls airdropped, unpowered explosive weapons "bombs," and such bombs are normally used by air forces and naval aviation. Other military explosive devices are called grenades, such as hand grenades), shells, depth charges, warheads when in missiles, or land mines.

They have been used for centuries in warfare and are a central part of a terrorist's arsenal. They fall into three distinct categories: conventional if filled with chemical explosives, dispersive if filled with submunitions, chemicals or other disruptive agents which are spread on or shortly before impact, or nuclear if relying on nuclear fission or nuclear fusion for their effect.