/ Dictionary / Index C coinstantaneous: Meaning and Definition of Find definitions for: co•in•stan•ta•ne•ous Pronunciation: (kō"in-stun-tā'nē-us), [key] — adj. occurring or existing at the same instant; simultaneous. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. coin silver coinsurance Related Content Daily Word Quiz: pedagogy Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language