[′sōd·ē·əm ‚bȯr·ō′hī‚drīd] (inorganic chemistry) NaBH4 A flammable, hygroscopic, white to gray powder; soluble in water, insoluble in ether and hydrocarbons; decomposes in damp air; used as a hydrogen source, a chemical reagent, and a rubber foaming agent.AcronymsSeeSBH