Terminology for words that are the same backwards and forwards, upside-down or right way up
Perhaps "palindromic rotational ambigram"? I just stuck "palindromic" on the front of "rotational ambigram".
I don't think there's a term with fewer than three words to describe what you want.
(I'm not sure the distinction from "rotational ambigram" is necessary, as most rotational ambigrams seem to be palindromic--I'm guessing designing those is just easier--but it's your language. More concise is okay, and more words are okay.)