The word scathingly 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: 21
Highest Scoring Words With Friends™ Play In The Letters scathingly
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Seven Letter Word Alert: (31 words)
alights, anglist, cashing, casting, chasing, clayish, ghastly, glitchy, glycans, halting, hastily, lacings, lashing, lasting, lathing, nastily, nightly, saintly, salting, scaling, scantly, shingly, sightly, slating, slaying, snatchy, snitchy, stagily, staying, stygian, styling