/ Dictionary / Index I instability: Meaning and Definition of Find definitions for: in•sta•bil•i•ty Pronunciation: (in"stu-bil'i-tē), [key] — n. the quality or state of being unstable; lack of stability or firmness. the tendency to behave in an unpredictable, changeable, or erratic manner: emotional instability. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: instability (Thesaurus) inst. instability line Related Content Daily Word Quiz: acquiesce Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language