an attack by dropping bombs the use of bombs for sabotage; a tactic frequently used by terrorists (a-bomb) atom bomb: a nuclear weapon in which enormous energy is released by nuclear fission (splittin [..]

(n) an attack by dropping bombs(n) the use of bombs for sabotage; a tactic frequently used by terrorists

The unlawful and intentional: 

air support

Dropping units on top of the enemy's units in order to cause splash damage from your own units (Banelings) or make the enemy's units attack themselves with splash damage (Siege Tanks).

A term referring to when a Soldier or Demoman explosive jumps above the enemy and shoots at them from above.