/ Dictionary / Index H helmet shell: Meaning and Definition of Find definitions for: hel'met shell" Pronunciation: [key] a predatory marine gastropod of the family Cassidae, characterized by a thick, heavy shell with a broadened outer lip. the shell of this animal, often used for making cameos. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. helmet liner Helmholtz Related Content Daily Word Quiz: endear Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language