The word thriftiness 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 thriftiness
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Seven Letter Word Alert: (34 words)
fishers, fishier, fishnet, fitness, fitters, hissier, hitters, infests, inherit, inserts, niftier, nitrite, nittier, reshift, resifts, retints, sherifs, shifter, shiners, shinier, shrifts, shrines, sifters, sinters, sitters, snifter, strifes, theists, thirsts, thrifts, tiniest, tinters, tintier, tithers