Is the damage calculated as Damage per Second or Damage per Hit?

Every weapon has a certain Damage. But they didn't tell us what it exactly means.
So, does the Damage mean Damage Per Second or Damage per Hit?

On quests, the weapon damage value is per-round. For weapons with a single hit per round this is easy. For multi-hit weapons (including multi-shot and AoE) the damage is distributed over each hit. Frequency of attack rounds is determined by Agility. The weapon damage is also scaled by Strength.

In the vault, weapons do damage constantly over time regardless of animations or damage type. The DPS should be a function of the average weapon damage and the dweller's Strength, Perception and Agility.

It's damage per hit. Your DPS is calculated using the weapon's damage and your special skills, but I don't have the exact formula.

Although the health bar may decrease over time when the weapon is firing, the total damage will be the damage rating of the weapon.

It's also worth adding that explosive or area of effect weapons, such as the MIRV, deal their damage split between all enemies in a room. For example, say you had a MIRV that did 30 damage and had 3 enemies in the room, they would each take 10 damage every time it fires.