Gastropoda n. pl. : One of the classes of Mollusca, of great extent. It includes most of the marine spiral shells, and the land and fresh-water snails. They generally creep by means of a flat, muscular disk, or foot, on the ventral side of the body. The head usually bears one or two pairs of tentacles. See Mollusca.

Example:


Taxonomy
gastropods, shell, species, marine gastropods, clade, snails, class Gastropoda, gills, land snails, ganglia, fossils, fossil gastropods, Sensory organs, terrestrial gastropods, slugs, tentacles, eyes, ranks.

Defination from the web:
... Main article: Taxonomy of the Gastropoda (Ponder & Lindberg, 1997) ...