The word carefulnesses 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: 22
Highest Scoring Words With Friends™ Play In The Letters carefulnesses
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Seven Letter Word Alert: (84 words)
ancress, assures, careens, careful, carless, caseful, causers, censers, censure, cereals, classes, clauses, cleaner, cleanse, creases, cresses, cussers, earfuls, earless, encases, enseals, ensears, ensures, essence, euclase, feelers, fencers, fescues, fleecer, fleeces, flenser, flenses, fuelers, funeral, furanes, furless, furnace, fussers, lancers, leaners, leasers, lessees, lessens, nuclear, recanes, reclass, reclean, recluse, recusal, recuses, refaces, refence, refuels, refusal, refuses, relaces, release, resales, rescale, rescans, rescues, reseals, sacless, saucers, scalene, scalers, sclerae, scleras, screens, sealers, seances, secerns, secular, secures, sensual, sucrase, sunless, surface, unclear, unlaces, unreels, unseals, ureases, useless