The word imposture 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: 16
Highest Scoring Words With Friends™ Play In The Letters imposture
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Seven Letter Word Alert: (28 words)
impetus, imports, imposer, moister, mopiest, mortise, mousier, mustier, permits, piteous, posture, pouters, poutier, primost, promise, restump, ropiest, soupier, spouter, spumier, stomper, stourie, stumper, toprims, tourism, troupes, umpires, uptimes