Honing is a final finishing operation conducted on a surface, typically of an inside cylinder, such as of an car engine block. Str8 from the book i add!
Basically if it hasnt been run in properly you can end up with odd tolerances in the block, the car should be run in by the book or you can end up with the scenario where at 70-80 mph or more you will get a droning noise from the car, this can be where the pistons aint sitting sweetly up n down the barrells as the car has only ever been used on slow runs. its commonly known as honing.