The word polyestrous 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: 18
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (63 words)
elusory, elutors, estrous, leprosy, leprous, loosest, looters, lotuses, lusters, oestrus, ospreys, ostlers, ousters, outsole, outyelp, oysters, petrols, plouter, polyose, poorest, poroses, poseurs, posters, posture, poulter, poultry, pouters, pulsers, pylorus, replots, reposts, respool, respots, results, retools, rustles, slopers, solutes, sourest, soursop, spooler, sporule, spouter, sprouts, spryest, sterols, stooper, storeys, stupers, stupors, stylers, stylops, sutlers, sutlery, systole, toolers, topless, toruses, tousles, toyless, troupes, tyloses, uproots