The word sluttishness 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: 17
Highest Scoring Words With Friends™ Play In The Letters sluttishness
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Seven Letter Word Alert: (26 words)
enlists, hussies, hustles, insults, listens, luniest, lushest, lutists, lutites, nutlets, shutins, shuttle, silents, sinless, sinuses, sleuths, slushes, sunless, sunsets, theists, thistle, tinsels, tissues, tussles, unlists, utensil