The word backslapper 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: 28
Highest Scoring Words With Friends™ Play In The Letters backslapper
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Seven Letter Word Alert: (26 words)
apparel, appeals, appears, backers, balkers, blacker, cablers, capable, carpals, carpels, clapper, clasper, packers, palaces, parable, parcels, placers, prepack, rappels, rebacks, reclasp, repacks, scalper, slacker, spackle, sparkle