The word sleepwalker 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: 23
Highest Scoring Words With Friends™ Play In The Letters sleepwalker
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Seven Letter Word Alert: (28 words)
keepers, kelpers, leakers, leapers, peelers, pleaser, presale, presell, relapse, release, repeals, repeels, respeak, respell, resweep, reswell, rewalks, skelper, sleeker, sleeper, spaller, sparkle, speaker, speller, sweeper, sweller, walkers, weepers