Somebody (often immature, a suck-up to a higher power,a
square, or a hyprcrite) who 'tells-on' or 'squeals' on other
people for doing something considered 'not right' or 'forbidden'.
'Dibber Dobber' is not an endearing term, and these
people are often disliked by others.
Thomas: "Are you guys supposed to be on
facebook at work?"
Catherine: "Well, not really but we're only having a quick look"
Thomas: "Well, i'm telling the
boss..."
Catherine: "Dibber Dobber!"