The word slothfulness 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 slothfulness
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Seven Letter Word Alert: (28 words)
ensouls, flosses, fluents, flushes, foulest, fullest, hostels, hostess, hotness, hustles, lessons, lossful, lotuses, lushest, outsell, sellout, sleuths, sloshes, slushes, softens, solutes, sonless, stollen, sulfone, sunless, sunsets, tousles, tussles