Definition: (noun) Any of various mollusks of the class Gastropoda, such as the snail, slug, cowrie, or limpet, characteristically having a single, usually coiled shell or no shell at all, a ventral muscular foot for locomotion, and eyes and feelers located on a distinct head. Synonyms: univalve. Usage: The sound of a shell crushing beneath his foot told him that he had just caused a gastropod's demise. Discuss