Leaving frozen meat out at room temperature overnight encourages the growth of bacteria in the meat as it thaws. Meat needs to be kept in temperatures below 40 degrees Fahrenheit.
It is never safe to defrost meat at room temperature. The best way to defrost meat is in the refrigerator. When time is a problem, microwave defrosting is a decent option. Another option is the cold water method of thawing in which the meat remains in its original packaging. If the packaging is not airtight, the package can be put into a bag that is airtight. The meat is placed in cold water deep enough to cover it, and the water is changed every half hour. Meat thawed using the microwave or cold water thawing methods needs to be cooked promptly. Re-freezing is not recommended.