The word extensional 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 extensional
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Seven Letter Word Alert: (39 words)
annexes, anoints, antlion, axstone, elastin, elation, elixate, enolase, enolate, entails, intense, intones, isolate, lateens, leanest, leantos, lenient, lenites, lineate, linnets, lionets, nailset, nations, neatens, neonate, nonlate, nonsale, oleates, oxalise, oxtails, salient, sealion, sextain, sextile, sixteen, tensile, tension, toenail, xennial