The word authenticities 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: 21
Highest Scoring Words With Friends™ Play In The Letters authenticities
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Seven Letter Word Alert: (43 words)
achenes, achiest, acutest, acutish, aitches, atheise, atheist, attunes, aunties, chasten, chaunts, cuisine, cuneate, ensuite, enthuse, entices, estuate, etchant, ethanes, ethnics, ichnite, incites, instate, intuits, neatest, nictate, nutcase, sinuate, situate, statice, statute, staunch, tautens, tautest, teaches, techies, testate, tetanic, tetanus, tiniest, titanic, unities, unteach