/ Dictionary / Index M mountain oyster: Meaning and Definition of Find definitions for: moun'tain oys"ter Pronunciation: [key] the testis of a calf, sheep, pig, etc., used as food. Also calledCf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mountainous mountain range Related Content Daily Word Quiz: cosmology Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language