The word underseals 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: 14
Highest Scoring Words With Friends™ Plays In The Letters underseals
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Seven Letter Word Alert: (40 words)
assured, asunder, dealers, duelers, earless, eldress, eluders, endears, endless, endures, enlards, enseals, ensears, ensured, ensures, landers, launder, leaders, leaners, learned, leasers, lenders, redeals, redness, resales, resands, reseals, resends, sanders, sealers, senders, sensual, slander, slender, snarled, sundaes, undress, unreels, unseals, ureases