The word cruciverbalist is relatively new; World Wide Words suggests that it first appeared in1981 in the title of a book, Compleat Cruciverbalist (http://www.worldwidewords.org/weirdwords/ww-cru1.htm). The subtitle of the book is "how to solve, compose, and sell crossword puzzles", which reveals the meaning of the word perfectly: a crossword enthusiast specifically, though more generally a word game enthusiast; and also one who constructs crosswords for fun or profit.
Cruciverbalist (or, more rarely, cruciverbalism for the art of crossword compilation or fandom) is a vox barbara, that is, a mock-Latin word. In fact, it's a translation from the English word crossword into Latin: crucis, cross, plus verbum, word.
Cruciverbalists can construct their own crossword puzzles, if they're Mac users, with a freeware program called, aptly, "Cruciverbalist"; it's available from Tucows at http://allmacintosh.xs4all.nl/preview/206066.html
And for Americans who need help solving crosswords use "Proverb: the Probabilistic Cruciverbalist", available from http://www.cs.duke.edu/~keim/proverb/
Introduced to my vocabulary from A.Word.A.Day, supplemented with additional information.