/ Dictionary / Index C cap rock: Meaning and Definition of Find definitions for: cap' rock" Pronunciation: [key] — Geol. Geol. a mass of anhydrite, gypsum, or limestone immediately above the salt of a salt dome. an impervious stratum overlying an oil- or gas-bearing structure. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. caproate caproic acid Related Content Daily Word Quiz: eccentric Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language