The word plethoras 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: 15
Highest Scoring Words With Friends™ Play In The Letters plethoras
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Seven Letter Word Alert: (28 words)
apostle, earshot, halters, hapters, harlots, holster, hostler, lathers, loather, loathes, palters, paroles, patrols, petrols, plasher, plaster, platers, portals, pothers, rathole, replots, seaport, slather, stapler, strophe, taphole, teashop, tephras