In the British National Scrabble Championship the final play was with the word "coniines," which neither of the finalists probably knew the definition of. Not all of the words on the board could be found in the Oxford English Dictionary, but they're still legal plays, thanks to the Scrabble Dictionary. The difference? Once a word gets in the Scrabble Dictionary, it never leaves, unlike outdated words that gets phased out.
Players tend to memorize a list of words without caring about the definitions. Many of the world's best Scrabble players are Thai that don't speak a word of English, but can spell it out pretty well. In fact, knowing English puts that player at a disadvantage.
Of course, if a house rule states you have to supply a ballpark definition, those world-class stars will fail miserably.
