crystalloidPronunciation: /ˈkrɪst(ə)lɔɪd/Definition of crystalloid adjective resembling a crystal in shape or structure. noun 1 Botany a small crystal-like mass of protein in a plant cell. 2 Chemistry a substance that, when dissolved, forms a true solution rather than a colloid and is able to pass through a semipermeable membrane. crystalloid in other Oxford dictionaries Definition of crystalloid in the US English dictionary