Noun
a 5,000 pound laser-guided bomb that can be programmed to penetrate to a given depth before exploding; used to penetrate hardened underground facilities
Source: WordNetGun barrels from retired M110s were initially used as the outer casing in the manufacture of the GBU-28 bunker buster bomb. Source: Internet
One of the more effective housings, the GBU-28 used its large mass (convert) and casing (constructed from barrels of surplus 203 mm howitzers ) to penetrate convert of concrete, and more than convert of earth. citation. Source: Internet