The word superclasses 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: 20
Highest Scoring Words With Friends™ Plays In The Letters superclasses
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Seven Letter Word Alert: (77 words)
alecups, asepses, asperse, assures, capless, capsule, carless, carpels, causers, cereals, clasper, classes, clauses, creases, cresses, cupless, cussers, earless, elapses, escaper, escapes, escarps, euclase, leapers, leasers, parcels, parsecs, passers, percuss, perusal, peruses, placers, pleaser, pleases, pleurae, plusses, presale, presses, pulsars, pulsers, reclasp, reclass, recluse, recusal, recuses, relaces, relapse, repaces, repeals, replace, repulse, resales, rescale, rescues, reseals, respace, sacless, sapless, saucers, scalers, scalper, sclerae, scleras, scrapes, scruple, sealers, secular, secures, serapes, spacers, specula, spruces, sucrase, surpass, upscale, ureases, useless