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.
Gastropods are the most diverse family of mollusks, including over 60,000 species of snails and slugs that live in marine, freshwater, and terrestrial habitats. Cephalopods, the most advanced mollusks, include octopuses, squids, cuttlefish and nautiluses. Most of the members of this group either lack shells, or have small internal shells.