A Japanese expression of confusion. Often used by otaku to indicate confusion/disorientation. People who read/watch "Rurouni Kenshin" may pick up the habit of saying "Oro!" because Himura Kenshin says it often in the manga/anime.
*after getting smacked in the head repeatedly* Oro! XD
it's a word used by the main protagonist, Kenshin, in the anime, Ruruoni Kenshin as an expression. it doesnt really mean anything in particular but it does get it's meaning from the manner in which the character says it.