An
emoticon intended to appear as a blushing person, the 'O's being eyes and the slashes (///) being the blush, similar to how it's represented in animes and cartoons.
It can
mean someone is flustered, embarrassed, and more things associated with blushing.
This
emotion can also be shown as O\\\O, O\\O, O//O, O//o, O\\o, and more similar variants.
Person A: Do you have a crush on him!?
Person B: Ehmm. O//O
Person A: I'm pretty
sure Jason heard about what you did before you sobered up at the party last
night.
Person B: Oh god. O///O. Kill meee