The word swarthiness 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 swarthiness
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Seven Letter Word Alert: (63 words)
answers, anthers, antsier, arshine, arshins, ashiest, assents, asserts, hairnet, harness, hastens, hastier, hernias, hissers, inserts, instars, nastier, rashest, rawness, resists, restain, retains, rethaws, retinas, sassier, satires, seitans, sestina, shiners, shrines, siestas, sinters, sisters, stainer, stashes, strains, swasher, swashes, swathes, swisher, swishes, tarnish, tawnier, tinware, trashes, twiners, waiters, wanters, wariest, washers, wasters, wearish, whiners, whitens, winters, wiseass, wishers, withers, witness, wraiths, wrasses, wreaths, writhes