The word unfasteners 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: 17
Highest Scoring Words With Friends™ Play In The Letters unfasteners
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Seven Letter Word Alert: (46 words)
austere, earnest, eastern, enfants, ensears, ensnare, ensures, euaster, fastens, fatness, feature, festers, fetuses, funnest, furanes, natures, nearest, neatens, nesters, neuters, refuses, refutes, renests, rennets, reseats, resents, retunes, sateens, saunter, seaters, senates, sensate, sterane, stunner, sunstar, suntans, tanners, teasers, tenners, tenures, unearnt, uneaten, unreset, unrests, unseats, ureases