Would it be unhealthy to ingest 5 and 1/4 cups of olive oil?

Diarrhea: You will have VERY loose bowel movement. Try not to do this routinely. Olive oil is healthy but in normal use as in cooking with it or in salads.

Yes: Not only would you likely wind up with a terrible case of diarrhea as it passes through you, you would be ingesting a huge amount of calories. One tablespoon of olive oil has 120 calories. So 5.25 cups of it equals 84 tablespoons which is 10,080 calories of pure fat in one shot!

Yes: if you did it because you are constipated soon you will not be.

5 + cups olive oil: I first would be interested in why you would want to do this. If you are constipated, this would take care of that problem. There is no way your intestinal tract would be able to absorb that much olive oil so most would come out the back end. I would not recommend doing this more than once, if that many times.