Pronunciation: (un-stā'bul), [key]
1. not stable; not firm or firmly fixed; unsteady.
2. liable to fall or sway.
3. unsteadfast; inconstant; wavering: unstable convictions.
4. marked by emotional instability: an unstable person.
5. irregular in movement: an unstable heartbeat.
6. Chem.noting compounds that readily decompose or change into other compounds.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.