The word proliferate 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 proliferate
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Seven Letter Word Alert: (45 words)
airport, alerter, earlier, etaerio, ferrite, fertile, firepot, fleapit, flirter, floater, foliate, forelie, frailer, leafier, loftier, operate, peatier, perlite, petiole, politer, praetor, prefile, prefire, prelate, profile, prorate, realter, realtor, reflate, refloat, relater, repilot, replait, replate, repleat, replier, reptile, retrial, taperer, tearier, toprail, trailer, trefoil, trifler, tripole