Breadcrumb Home > Dictionary > Index I instable: Meaning and Definition of Find definitions for: in•sta•ble Pronunciation: (in-stā'bul), [key] — adj. not stable; unstable. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. instability line instal ✖ Related Content Daily Word Quiz: rococo Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language