The word obsolescing 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 obsolescing
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Seven Letter Word Alert: (39 words)
belongs, bigness, binocle, boogies, bosonic, bossing, cession, closing, cobless, cognise, cologne, colossi, console, cooling, cosigns, cosines, ebonics, eloigns, glioses, goblins, goosies, ignoble, insoles, isogons, legions, lesions, lingoes, lioness, loonies, loosens, loosing, losings, obliges, oblongs, oleosin, oncosis, ossicle, singles, soloing