You're home and forgot to defrost something for dinner. You grab a package of meat or chicken and use hot water to thaw it fast. Neither of these situations are safe, and these methods of thawing lead to foodborne illness.
Foods are safe indefinitely while frozen.
However, as soon as food begins to defrost and become warmer than 40 F, any bacteria that may have been present before freezing can begin to multiply. Foods should never be thawed or even stored on the counter, or defrosted in hot water. When thawing foods in the refrigerator, there are several variables to take into account. Some areas of an appliance may keep the food colder than other areas. Food placed in the coldest part will require longer defrosting time.