. Chemistry: Rate at which a chemical will evaporate. Volatility increases with temperature and decreases with pressure. Latin for, to fly away.
2. Economics: Rate of change in price over a given period. Expressed often as a percentage, it is computed as the annualized standard deviation of the percentage change in the daily price.
3. Securities trading: Size and frequency of rapid changes in the price of a security. If the causes of volatility are peculiar to security, it is measured by alpha; if the causes are related to the securities market as a whole, it is measured by beta.