According to Craig Rowland, Scrabble in North America recognizes five words which, if spelled over two triple-word score squares, and with a premium-scoring tile on the double-letter score square, will award the player 392 points on a single play. These five words are: OXAZEPAM, BEZIQUES, CAZIQUES, MEZQUITS, and MEZQUITE.Link Discuss (Thanks, Gary!)
John Chew says that OXYPHENBUTAZONE is the highest-scoring word known under American tournament Scrabble rules (OSPD+MWCD). It can score 1778 under suitably contrived circumstances listed and credited in the Scrabble FAQ.
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects