1. U.S. Navy.a seagoing, amphibious ship capable of carrying and launching assault landing craft from a large, inner compartment that can be flooded, and of making emergency repairs at sea to smaller ships.
2. Pharm.lysergic acid diethylamide: a crystalline solid, C20H25N3O, the diethyl amide of lysergic acid, a powerful psychedelic drug that produces temporary hallucinations and a schizophrenic psychotic state.
3. See least significant digit.