The word carbonaceous 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 carbonaceous
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Seven Letter Word Alert: (32 words)
accrues, accurse, accuser, acerous, beacons, bescour, boranes, bouncer, bounces, broncos, buccans, caboose, cancers, canoers, carbons, carouse, coarsen, concurs, corncob, corneas, coronas, cubanes, curacao, obscure, onerous, raccoon, racoons, rosacea, subarea, subrace, unbrace, unrobes