I mean, seriously, of course there is such a word as 'deplane' -- just because one dislikes it doesn't mean it is not a valid word. I know what it means to deplane, and most English-speakers will also know it's meaning; it certainly seems to fit the criterion for being a word. Whether or not a word is a word is not limited to it's appearance in a certain edition of a specific dictionary! What a dull world it would be if language was static.
My point is that it's an unnecessary word. A word already exists to describe that concept - "disembark," as Macleod says. I'm all for new words to describe new concepts. Of course Chaucer didn't have a word for "internet," because he didn't need one. Likewise there's no need to create a new word to describe "disembark" when there's already a perfectly good word that serves the purpose. After seven years of living in the States, I have to say my impression wasn't that it was a dialectal difference, but rather ignorance of the fact that the word "disembark" exists at all.
Likewise, usage of such non-words as "winningest" on Nascar commentary makes me want to stab a bitch.
"Guess" and "estimate" are so similar in meaning anyway that nothing is gained by combining them that couldn't be described perfectly well by one or the other. It's utterly pointless.
"Guess" and "estimate" aren't the same thing. An estimate is an approximate calculation. A guess is something you pull out of your ass.
I never said they were identical - I know they're not. But what possible middle ground is there between the two that requires a whole new word to describe it? Either something is an educated calculation (thus an "estimate") or it's not (thus a "guess").
It's like when people say "more unique." Impossible!
"Unique" is an absolute state, it is not subject to gradation.