Usually said in a derogatory or dismissive way, as if to insinuate that something shown or mentioned, is of no real interest at all, has been seen before, even, or especially when the item is brand new, unique and very splendid
Andy showed Chris his brand new, custom made wanking mitt
Oh THAT wanking mitt... said Chris
The word used in the exact moment when one's own stupidity is realized.
Don't eat that! It's toxic!
...oh.
means that ur just so over everythig and u cant do anything bc ur too sad and cant do anythig and all you can do is say oh
dog: woof
you: hewow you cute doggie
mum: the dogGie isnt rEal
you: oh
scotland: when you are shocked!
person 1: i really like scott!
person 2: oh there!
Oh no, our table, it's broken!
Dave: Dude, my brother just Oh no! Fred: Congrats.