Nathan Fillion created the phrase: Dubul Rynbo as an alternate spelling of Double Rainbow.
It means that which is:
Here are some paraphrased usage examples of Dubul Rynbo including some from NathanFillion on his Twitter page:
"Why is the iPad so Dubul Rynbo? (Double Rainbow)"
Answer to why is Nathan Fillion so awesome? "Because he's Dubul Rynbo (Double Rainbow) All The Way."
The TV series Firefly is so intense, it's Dubul Rynbo! (Double Rainbow!)