Paul Allan, 43, nailed the victory four games into a nail-biting five-game series against Borders-based Allan Simmons by collecting a total of 86 points for "bandura".
As well as introducing many in the audience to the word - it's a kind of Ukrainian lute - he pocketed £2500 in prize money.
After his victory in London, the Aberdonian admitted to having an "end of exam feeling".
He said: "I'm just glad it's over because you're thinking about it all the time leading up to it, so it's nice to be able to relax now.
"I wasn't that nervous beforehand. When you're actually playing the game you're generally OK, but when I picked a blank in the fourth game I got quite nervous and I made a mistake."
His exam metaphor is apt: his revision for the big day involved going over and over the many thousands of words he has in his head in order that they would spring readily to his fingertips. Luckily they did.
He said: "You have to know 150,000 words. I've already been through all the words that are eight letters long, that's about 110,000, then you have all the extension, which take you up to the 150,000.
"But you're keeping them topped up by reviewing them at about 2000 words a day. I do that on the computer."
Among the other not-so-everyday words which featured in this year's final were: kernite (a mineral), mete (meaning to measure), portage (a bridge toll), valerate (a chemical salt), shrieval (relating to sheriffs), exordial (meaning to begin) and coniines (a poisonous alkaloid found in hemlock).
Mr Allan, who met his Japanese wife through an online Scrabble forum, now lives in Rushden in Northamptonshire where he works as a teacher.
This isn't the first time that he's scooped British Scrabble's top prize either: in 2007 he won with the word "ai" (a three-toed South American animal, though also the Japanese word for love).
Other words he used on the way to that 2007 win were "fatwa" (a legal judgment given by an Islamic jurist) and - one that needs no explanation - "bum".
On his way to this year's final he defeated 57 other players at the semi-final in Cardiff and will now compete in the World Scrabble Championships in Prague next month as part of the Scottish team.
His 56-year-old opponent, Allan Simmons, is originally from Kent but now lives in Coldingham where he makes a living as a Scrabble consultant and author of books about Scrabble.
Among the tomes to which Mr Simmons has contributed is the Official Scrabble Words dictionary, an aa to zythums of the more arcane and esoteric end of the lexicological spectrum - but devilishly handy if it's your go and there's a triple word score just begging to be filled.
Though he lives in Scotland, Mr Simmons will also take part in the World Scrabble Championships as a member of the English team.
While Scrabble is likely to remain a simple kitchen table board game in this country for some time to come, it is a far bigger deal elsewhere in the world.
Mr Allan said that the game was a big stadium event in Thailand.
He said: "English language Scrabble is a standard part of the curriculum there.
"They think that it helps language, numeracy and maths skills.
"You go there and there are tournaments with over 10,000 kids playing, whole stadiums full of them. It's a big deal there."