GBU-28 gbu uncommon noun 1. a 5,000 pound laser-guided bomb that can be programmed to penetrate to a given depth before exploding; used to penetrate hardened underground faccilities SynonymsBunker BusterGuided Bomb Unit-28 Related words Broader terms laser-guided bomb WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
