The word nefariously 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 nefariously
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Seven Letter Word Alert: (34 words)
aileron, earfuls, elusion, elusory, failure, finales, flayers, florins, forelay, funeral, furanes, infuser, infusor, inlayer, insofar, insular, inulase, loafers, loaners, lousier, nailers, olefins, orleans, ourself, refusal, reloans, renails, reunify, sealion, sulfone, unlayer, unleafy, urinals, yearful