What is the definition of Volatility in Stock Market or In Investment?

In an easy term, Volatility means frequent fluctuation. For example, some stocks fluctuate a lot, mean, the stock prices change so much that the value of the company changes randomly or frequently. 

By textbook definition, volatility refers to the size of changes in the price of an asset. In a more technical sense, it is a measure of the deviation of returns for a given asset. If an asset is very volatile then its price is likely to change a lot. The measure of volatility provides no indication as to the direction of change, merely the amount.