The word echinoderms 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: 21
Highest Scoring Words With Friends™ Play In The Letters echinoderms
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Seven Letter Word Alert: (83 words)
ceroids, cheerio, chimere, chromed, chromes, cinders, codeine, coheirs, cohered, coheres, coiners, crimson, cronies, deciohm, decries, dehisce, dehorns, deicers, demonic, deniers, denoise, diocese, discern, dishorn, dormice, echoers, encoder, encodes, encored, encores, endemic, endorse, heroics, heroine, heroins, heroise, heroism, hinders, homered, inchers, incomer, incomes, indorse, inshore, isomere, menders, mercies, meshier, microns, mincers, minders, miocene, miscode, misdoer, misdone, moderns, moschid, necrose, nimrods, nordics, orchids, rechime, rechose, recodes, recoins, rehides, rehomed, rehomes, rehoned, rehones, remends, reminds, remined, remines, rescind, reshine, reshoed, rosined, schemed, schemer, scorned, shrined, sincere