What is a Block Buster?

That was an informal name for a large bomb. I'm not sure just how big a bomb had to be before it might be called a blockbuster, at least 500 lbs, maybe as much a 2000 lbs (this was informal so there was no hard and fast rule). The name derived from the idea, more hyperbole than reality, that the bomb could destroy an entire city block. Michael Montagne The 'blockbuster' bombs got bigger during WW2 as the bombers were able to carry heavier bombs. Early in the war a 4,000 lb bomb (just under two tons) was rated a 'blockbuster'; towards the end of the war the heaviest (conventional) bombs weighed 22,000 lbs (= 10 tons).