What is O Dear?
when somebody says something so utterly stupid that it simply has to be shouted sarcastically accross the room
aimee: are polar bears made out of fibre-glass?
frank: O DEAR!!!
Being shocked beyond all reason and no other words that can escape your mouth.
Can be used to express shock, grief, amazement, disbelief, annoyed, etc.
Guy 1: Who is Chuck Norris?
Guy 2: Are you serious?
Guy 1: Yea.
Guy 2: O dear.