Educated Wild-Ass Guess
A guess where you don't know the answer, but you do know something about the subject in general, so your answer will be better than just a WAG (Wild-Ass Guess).
Bob: Hey John, what's a Drosophila melanogaster.
John: Not sure. From my extensive knowledge of ancient Greek I can tell you "Drosophila" means "dew lover" and "melanogaster" means "fruit-eater". My EWAG would be some kind of fruit eating bug.
Bob (under breath): "What a Putz. I'll just look it up on wikipedia."
Estimated Wild Ass Guess. Used in the military. Similar to FUBAR
me: i'm logged into gmail 50 hours a week...
Cindy: it records that?
me: no, that's an EWAG