The word frighteningly 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: 27
Highest Scoring Words With Friends™ Play In The Letters frighteningly
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Seven Letter Word Alert: (51 words)
enlight, felting, fierily, fighter, firelit, flighty, freight, gifting, gingery, girling, girning, greying, heftily, hefting, hinging, hinting, igniter, inertly, inherit, lengthy, lifting, lighten, lighter, lignify, lignite, lintier, lithify, niftier, niftily, niggler, nightie, nightly, ninthly, nitrify, reining, relight, relying, renting, retying, rifling, rifting, rightly, ringgit, ringing, ringlet, thinner, tiering, tinging, tingler, tinnier, tinnily