Volatility is a term borrowed from investing in finance that is used to describe large swings in price.
Cryptocurrencies as a whole a considered to be volatile assets because their prices can fluctuate more than +/-10% in either direction in one day.
Volatility is seen as a great thing for traders because it shows opportunity for large financial gains in short time frames; whereas for inexperienced investors, it is seen as a deterrent due to the uncertainty present in the pricing of assets.