How long does meat stay good after it is defrosted?

When determining how long thawed food will be good, you have to remember that decomposition will pick up from where it left off when the food was frozen. How long it took to freeze will have a bearing on it, too.

If the ground beef was 3 days old when frozen, you might try cooking it from frozen. If it was freshly ground when frozen, the thawed meat will likely be good for 2 days.
Once thawed, the ground meat should be used within a day or two. Ground meat spoils quickly since grinding the meat mixes bacteria throughout.