How should fresh pork be thawed?

Fresh pork may be thawed in one of three ways: in the refrigerator, in cold water, or in the microwave. Never defrost fresh pork at room temperature. Surface areas will thaw at a quicker rate than interior areas, leaving them vulnerable to bacterial growth once they reach a temperature of 40°F. 

• Refrigerator: Once fresh pork defrosts, it can remain in the refrigerator for 3-5 days, assuming it was frozen immediately upon purchase. A small roast requires 3-5 hours per pound to defrost, a large one 4-7 hours per pound. A 1-inch-thick chop requires 12-14 hours. Package thickness determines the amount of time required to defrost ground pork. If you decide not to  use the pork, you can safely refreeze it within 3-5 days if it has remained refrigerated. 

• Cold water: Do not remove packaging when defrosting pork in cold water. Be sure the package is airtight, or put it into a leak-proof bag. Fully submerge the pork and change the water every 30 minutes so that it remains cold.

• Microwave: Cook the pork immediately after defrosting, as some areas may become warm and begin cooking during microwaving. Holding partially cooked food isn't recommended because any bacteria present may still be active.  
• Never refreeze pork that has thawed to a temperature greater than 40° F.  Freezing will inactivate but not kill any bacteria that may have accumulated as a result of completely thawing the pork. If pork has been thawed and warmed to room temperature, it should be cooked immediately. 

 
You can refreeze raw pork (or any other meat) that has been thawed in the refrigerator and has never reached room temperature.  However, there may be some quality loss because of fluid that drips out when the product is again defrosted.  (When water in food freezes, it forms crystals that puncture cell walls and allows them to leak.)
 
Source(s):
USDA Fact Sheet "Safety of Fresh Pork...From Farm to Table"
National Pork Board "All About Pork"
Susan Brewer, Ph.D.  University of Illinois, Department of Food Science and Human Nutrition
USDA  “Food Safety, Food Storage, Preparation & Handling.  Common Food Safety Questions”