It's called 'Greek style yogurt' sometimes but whatever you call it, it's not in fitday.
The best thing is to just take the nutrition information from whatever you are using and enter it as a custom food. There's 0%,1%,2%, and full-fat Greek yogurt, so that's another wrinkle in getting the information. Not to mention flavored and low-fat varieties. I don't know if one entry can stand in for any 0% Greek yogurt (for example.) It could be that the differences are so small that one entry can be used.
Basically, it's yogurt that has been drained to lose moisture content, which makes it thicker and higher in protein.