Definition of 'Naked Option'
A trading position where the seller of an option contract does not own any, or enough, of the underlying security to act as protection against adverse price movements. If the price of the underlying security moves against the trader, who does not already own the underlying security, he or she would be required to purchase the shares regardless of how high the price is. The potential for losses, then, can be unlimited, and as a result, brokers typically have specific rules regarding naked trading. Inexperienced traders, for example, would not be allowed to place this type of order.
Investopedia explains 'Naked Option'
Naked trading is considered very risky since losses can be significant. An options trader could sell, for example, call options with a strike price of $10. If the stock's price rises to $20 or $30 on good news, and the option is naked (the seller does not own the underlying stock). He or she would be required to buy the specified number of shares at the current price, and sell them to the option buyer for the $10, resulting in a significant loss.
Want to know more? Read Naked Options Expose You To Risk