A golf ball size amount of snot that is hacked up from the deepest part of your lungs. Similar to a loogie but with much more mass. A lung bomb can be considered as a lethal weapon in some States. The lung bomb will consist of thick mucus that is green, yellow and black in color. The blackness is either from a smokers lung or from dried up blood in the nasal cavities.
While on top of the Empire State Building:
Johnny: Hey let's drop some loogies off the side of this beast and get the people down below.
Rich: Hell yeah if I'm lucky I might be able to spew up a lung bomb for those suckers down below.
Johnny: Man I feel sorry for the sucker that get's nailed by that.