If an aircraft dive-bombs a place, it flies down steeply toward the ground and drops bombs as it comes in — a sudden, aimed attack from above, not bombs released from high, level flight. The word comes from war, and that is still the core meaning. Though actually, people later used the same picture for birds that shoot down at you (gulls at a picnic) and, jokingly, for a person who jumps onto a sofa or into a pool. The shape of the action stays the same: come down fast from above. It is a verb, usually written with a hyphen: dive-bomb.