The word nefariousness 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 nefariousness
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Seven Letter Word Alert: (51 words)
arouses, assures, ensears, ensnare, ensures, faeries, finesse, fissure, forseen, freesia, funnier, funnies, furanes, fusions, fussers, fussier, inferno, infuser, infuses, infusor, insaner, insofar, insures, issuers, neurons, nonfire, nonfree, nonuser, noseans, oneness, osseins, reasons, refines, refuses, reissue, reunion, sassier, seasons, seniors, sensors, serious, session, siennas, sinners, sinuses, soirees, sunnier, sunnies, sunrise, unrisen, ureases