The word peritonitis 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 peritonitis
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Seven Letter Word Alert: (41 words)
inosite, inspire, intorts, ioniser, ironies, nitrite, nittier, noisier, norites, orients, pietist, pitiers, pointer, portent, postern, potters, potties, pronest, protein, protest, protist, pterins, repoint, retints, ropiest, snotter, spinier, spotter, stipite, stonier, tiepins, tiniest, tinpots, tinters, tintier, tipsier, tipster, tiptoer, tiptoes, triones, tropist