The word inestimable 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: 19
Highest Scoring Words With Friends™ Play In The Letters inestimable
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Seven Letter Word Alert: (44 words)
ailment, albites, alibies, aliment, ambient, animist, astilbe, baleens, basemen, batsmen, beamlet, beanies, beslime, bestman, betimes, bimetal, elastin, elitism, enables, enamels, entails, iambist, inmates, itemise, laments, lateens, leanest, lenites, lesbian, libates, lineate, mantels, mantles, matinee, meanest, meanies, miniate, nailset, netmail, salient, seminal, tenable, tensile, timbale