The word apatosauruses 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: 18
Highest Scoring Words With Friends™ Play In The Letters apatosauruses
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Seven Letter Word Alert: (50 words)
arouses, assarts, asserts, assorts, assures, aurates, auteurs, estrous, oestrus, ousters, outraps, outspar, passers, passout, pasters, pastors, pasture, poseurs, possets, posters, posture, pouters, pursues, repasts, reposts, respots, russets, sarapes, satraps, seaport, searats, seastar, soapers, sourest, sparest, spouses, spouter, sprouts, stupers, stupors, surpass, sutures, toruses, tossers, tossups, troupes, trusses, uprates, uprouse, urostea