1. the quality or state of being unstable; lack of stability or firmness
2. tendency to change rapidly and unpredictably, especially in emotions or behavior
3. lack of physical balance or structural soundness

Examples

• Political instability in the region has affected economic growth.
• The patient showed signs of emotional instability after the trauma.
• Engineers were concerned about the structural instability of the old bridge.
• Market instability caused stock prices to fluctuate wildly.
• The instability of the ladder made it dangerous to climb.
• Weather instability led to sudden storms throughout the week.