I know that if you slice a raw onion, you can freeze it. I was?!
Answers: wondering, if you thaw it out to use some, is it safe to refreeze the rest or can you get sick from it?
I always chop up 4-5 onions and put them in a freezer bag. Just shake out what you need for cooking and put the bag back in the freezer. It's a real time saver. I've been doing this for years, no problem.
Yes it is same as long as you defrost it in the fridge. I would suggest when you do defrost it you should separate the onions into smaller portions before refreezing so you dont have to defrost then refreeze several times.
Bacteria grows at temperatures above 5 degrees c. As onion is not a high risk food it is ok to defrost and refreeze but I wouldnt do this with any meat or other high risk foods.
If you thaw a frozen onion you can refreeze it safely. The texture may be a little less crunchy the next time you use it. Of course if you refreeze those slightly thawed onions will stick together once they are refrozen BUT the refreezing has nothing to do with food safety.
Safety comes from how those original frozen onions are handled once they were thawed --how many hours, how clean was the container they were in, what was the air environment around the thawed onions. If they were only out at room temperature for 30 to 60 minutes and were then refrigerated they could be refrozen safely within 24-48 hours in the refrigerator.