that word does not exist!! "nan darou"!! and there is no direct translation for "oh geez"...other than knowing that for "gee..thanks"...it is ma arigato.

The japanese word for "Oh Geez" would be "mataku" またく

Seeing how you watch naruto, I think you might like to know how Shikamaru says it? shikamaru always says: how troublesome, which is "MENDOKUSAI" めんどくさい　in japanese.

Oh geez is more of a word to express tiredness because others are being a nuisance. In naruto and other anime I've watched, mataku is said quite a lot of times.
However, none of my dictionaries could find it. Im 100% sure this was the word you were looking for, because I tend to use it for "geez" a lot too.

Tains,

I believe the word you're thinking of is "mattaku" (note the double "t" ) which means entirely, really, wholly, truly, etc., depending on the context. You probably didn't find anything in the dictionary because you were looking up "mataku" (single "t" ).

I guess it's possible that said with the right tone of voice, "mattaku" might convey something like what "oh geez" does in English, but I think it is a stretch to call it "the translation" of this phrase.

*kind of off topic* AAHHH! SHIKAMARU is so AWESOME! *does the rat hand seal* hahaha!

*has to go to the career center today for a college program thing (we go around looking at colleges to better prepare us for the future AND BUILD ROCKETS!! I call it rocket science...and we get to shoot them off in front of wal mart, supposing they'll hit somebody, out rocket science teacher is hilarious*

I'll write more about my day later! Although, I think because of me, this topic has been going off topic...hahaha

Ah so thats how it was. 全く
indeed now I've found it. The translation "really" fits "oh geez" pretty fine in my opinion.

The reason I said this is simply because its said a lot in naruto, and it is said exactly in the way gaaragaara intended. Even more important: it is always translated as: geez.
I remember another word that was translated with "geez"(I always write japanese words and sentences down to translate them afterwards, and I remember most of them). たげ or something that sounded like Tage. As I said, these were words I couldnt find in my dictionaries, so I dont know their real meaning. The only thing I do know, is that they are used in both naruto as ergo proxy as a lot of other anime, and they are used as "geez".

-Tains