The word tropopause 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 tropopause
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Seven Letter Word Alert: (28 words)
apposer, opposer, outraps, outsoar, outspar, papoose, pasteup, pasture, paupers, poopers, poorest, posture, pouters, propose, pupates, purpose, seaport, spouter, stooper, stopper, support, tappers, toppers, toprope, troupes, uprates, uproots, urostea