Definition
The extent of variation in prices or returns, not a synonym for upside potential or loss probability.
Hypothetical example
Two paths may both start and end at 100; a path spanning 80–120 fluctuates more than one spanning 99–101.
Keep in mind
Use comparable periods and measures. Low historical volatility does not guarantee low future risk.
Official reference
www.finra.org ↗Examples are illustrative assumptions, not investment recommendations.