1. a very large amount of sth, or lit. a bus/truck full of sth
a bus/truckload of people/boxes/computers
This idiomatic expression is a good example of 'hyperbole' or using exaggeration for stylistic effect. It is used as a way of expressing a magnitude or colossal amount of something. You would be more likely to hear 'a busload' to refer to a large number of people: "We were just about to close the cafe when a busload of people arrived looking for coffee and sandwiches." A 'truckload' might refer to objects or materials: "I was amazed by the truckload of donations made during our appeal for food last year." These are not literal expressions and it is generally accepted that they are used for effect, usually in colloquial or social situations.