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, of course! Sea shells are the left-behind external skeletons of mollusks. Mollusks are small invertebrate animals that usually have delicate, slimy bodies. As mollusks grow, their shells protect their fragile bodies from the elements and predators that hunt them.