To defrost carries two everyday meanings. The first is to remove the ice that has formed inside a refrigerator or freezer — scraping, melting, or running a defrost cycle so the appliance cools efficiently again, since thick ice insulates the coils and wastes energy. The second is to thaw frozen food, bringing it from frozen to chilled or room temperature for cooking. Both senses turn on controlled melting, and the food-safety rules for the second are strict: defrost in the refrigerator, under cold running water, or in the microwave with immediate cooking — never at warm room temperature, where the surface enters the bacterial danger zone while the centre is still frozen. Modern frost-free appliances automate the first job with timed heater cycles; the second remains the cook’s responsibility and one of the most common points of failure in home food safety.