The word authenticates 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: 20
Highest Scoring Words With Friends™ Play In The Letters authenticates
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Seven Letter Word Alert: (48 words)
acetate, achenes, achiest, actants, actuate, acuates, acutest, acutish, aitches, atheise, atheist, attache, attains, attunes, aunties, caseate, chasten, chateau, chaunts, cuneate, ensuite, enthuse, entices, estuate, etchant, ethanes, ethnics, hastate, instate, nautica, neatest, nictate, nutcase, satanic, satiate, sinuate, situate, statice, statute, staunch, tautens, tautest, teaches, techies, testate, tetanic, tetanus, unteach