Defrosted ground beef can be refrozen if it was thawed in the refrigerator but not if it was left out and thawed in cold water. If it was thawed in cold water, cook the ground beef before refreezing it.
To safely thaw ground beef, put it in the refrigerator, and let it thaw cold. This takes longer, but it helps to prevent growth of bacteria and allows the option of putting it back in the freezer. After thawing it in the refrigerator, it needs to be cooked or frozen within one to two days. If thawing ground beef in cold water, wrap it in plastic, and submerge it in cold water. Change the water every 30 minutes.