The word economists 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 economists
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Seven Letter Word Alert: (27 words)
cession, consist, cooties, cosiest, cosines, emotion, incests, incomes, insects, mitoses, moisten, motions, noisome, nosiest, notices, oecists, oncosis, osmotic, osteons, section, sitcoms, somites, somonis, soonest, stomies, tocsins, toonies