Beluga!

Beluga is one of those family words or phrases which serve the marriage-preserving purposes of giving you a shorthand to use with each other and defusing a potentially aggravating or insulting situation by turning it into a joke. This is how it works.

Husband (for it is usually he) has been asked for information. He doesn't know, but he gives such an authoritative answer that Wife believes that he does know and that his answer is 100% accurate. Within a few minutes she realises he has no idea and just made up his answer (Husband innocently believes that his opinion is valuable, while Wife wants only good, solid facts). It is at this point that Wife exclaims, "Beluga!" in the spirit of, "Thar she blows!". The statement, "You don't [expletive deleted] know!" may be added, provided this is said and accepted with good humour.

Thus, a beluga is the act of stating an opinion so authoritatively that listeners are taken in and accept it as fact, while the speaker is devoid of knowledge on the topic.

The reason why beluga was chosen for this has been lost in the mists of time. We suspect that Wife asked Husband about whales, maybe whether beluga babies start black and turn white, or start white and turn black. A beluga occurred and over time, "Beluga!" came to be used as a shortened form of, "That's exactly what you did when I asked you about the beluga".

So we offer up this word for public use. We mentioned it to a couple of friends, who told other friends.... it would be interesting to know how far it's spread. And it's interesting that other couples know exactly the situation it describes.