In`sta*bil"i*ty (?), n.; pl. Instabilities (#). [L. instabilitas: cf. F. instabilité.]

1. The quality or condition of being unstable; want of stability, firmness, or steadiness; liability to give way or to fail; insecurity; precariousness; as, the instability of a building.

2. Lack of determination of fixedness; inconstancy; fickleness; mutability; changeableness; as, instability of character, temper, custom, etc. Addison.

Syn. -- Inconstancy; fickleness; changeableness; wavering; unsteadiness; unstableness.

• A state in which conditions are likely to change.
  
• (physics): Condition in which weight or force is not balanced.