The word cumbersomeness 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: 28
Highest Scoring Words With Friends™ Play In The Letters cumbersomeness
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Seven Letter Word Alert: (55 words)
becomes, bemuses, bescour, beseems, bonuses, boreens, bouncer, bounces, bummers, censers, censors, censure, cerumen, combers, commune, consume, courses, cresses, crosses, crubeen, cumenes, cussers, emerses, enbuses, encores, enrobes, ensures, essence, members, mousers, mousses, muscone, necrose, numbers, obscene, obscure, recombs, recuses, rescues, resnubs, resumes, ruesome, screens, secerns, secures, sensors, sermons, sources, sucrose, summers, summons, umbones, uncross, unrobes, urnmoss