The word oysterfish 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: 17
Highest Scoring Words With Friends™ Play In The Letters oysterfish
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Seven Letter Word Alert: (25 words)
fishers, fishery, foister, forests, forties, fosters, history, hosiers, hosiery, isohyet, oysters, reshift, resifts, rosiest, sherifs, shifter, shrifts, shyster, sifters, softies, sorties, storeys, stories, storify, strifes