The word slumbering 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™ Plays In The Letters slumbering
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Seven Letter Word Alert: (34 words)
bingers, blueing, blunger, blunges, buglers, bulgier, bungler, bungles, burling, busgirl, emulsin, erbiums, gerbils, girnels, gremlin, grumble, imburse, legumin, limbers, lingers, lumbers, mingler, mingles, misrule, mungers, nimbler, numbers, reusing, rulings, rumbles, slinger, slumber, suberin, sublime