The word unstoppable 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: 23
Highest Scoring Words With Friends™ Plays In The Letters unstoppable
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Seven Letter Word Alert: (45 words)
abluent, ablutes, apostle, applets, butanes, butanol, eluants, laptops, leantos, leptons, lunates, nebulas, nepotal, noblest, notable, opulent, outleap, outplan, outspan, papules, pasteup, peanuts, penults, petnaps, planets, plutons, potable, pueblos, pulsate, pupates, subnote, subplot, subtone, sunbelt, taboule, topples, topspun, tunable, unbales, unbelts, unblest, unbolts, upbeats, upslant, upslope