The word diagonalizing 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: 30
Highest Scoring Words With Friends™ Play In The Letters diagonalizing
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Seven Letter Word Alert: (24 words)
anginal, angioid, angling, dialing, dinging, gaining, ganglia, gaoling, gilding, glazing, gliding, glozing, goading, goaling, gonadal, landing, loading, loaning, lodging, longing, nailing, zingani, zingano, zinging