The word diagonalize is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 25
Highest Scoring Words With Friends™ Play In The Letters diagonalize
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Seven Letter Word Alert: (22 words)
adonize, aeolian, agonize, aligned, angioid, anilide, anodize, dealign, dealing, dialing, diazane, diazine, diazole, eliding, geoidal, gonadal, idolize, ionized, leading, lionize, loading, zenaida