Volatility refers to the likelihood of fluctuation in value. If the volatility of a product is high, it means that the value of the product may change significantly. If the volatility of a product is low, it means that the value of the product will only change slightly.
The volatility of Bitcoin is about three to five times the volatility of the dollar-yen exchange, so its volatility is greater than the dollar-yen rate.
In general, risk level of a product can be quantified in terms of the standard deviation of its volatility. In general, high volatility means high risk and low volatility means low risk.