The word slipperwort 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™ Plays In The Letters slipperwort
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Seven Letter Word Alert: (50 words)
estriol, loiters, loppers, lorries, owliest, petrols, plowers, plowter, politer, porters, potpies, preplot, presort, propels, prosper, prowler, repilot, replots, replows, reports, resplit, rioters, rippers, rippler, ripples, ripplet, ripstop, roister, ropiest, slipper, soppier, spoiler, stipple, stopper, striper, swirler, swopper, tippers, tippler, tipples, toilers, toppers, topples, triples, tripole, tripper, trowels, twirler, worries, writers