The word threadiest 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: 13
Highest Scoring Words With Friends™ Play In The Letters threadiest
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Seven Letter Word Alert: (63 words)
adheres, aeriest, aridest, artiest, astride, atheise, atheist, attired, attires, dearest, dearies, dearths, diester, dieters, diether, disrate, dithers, earthed, hardest, hastier, hatreds, hatters, headers, headier, headset, hearsed, hearted, heaters, heisted, hitters, iratest, iterate, rattish, readies, reasted, redates, reedits, reheats, rehides, restate, retaste, sedater, seriate, shadier, shatter, sheared, shirted, started, striate, tartish, tasered, tastier, testier, tethers, theater, theatre, thereat, threads, threats, tirades, tithers, trashed, treated