Nitric oxide (NO) Nitric oxide (NO), colourless, toxic gas that is formed by the oxidation of nitrogen. Though it has few industrial applications, nitric oxide performs important chemical signaling functions in humans and other animals and has various applications in medicine.
or British mollusc /ËmÉËlÉsk/. plural mollusks. Learner's definition of MOLLUSK. [count] biology. : any one of a large group of animals (such as snails and clams) that have a soft body without a backbone and that usually live in a shell.
Mollusks consist of a wide range of invertebrate animals, from snails to giant squids. A mollusk usually has a soft body that is covered with an exoskeleton, such as the shell of a clam. Just what sort of animal qualifies as a mollusk is up for debate, with some research classifying 50,000 species and others up to 200,000.