The word collarbones 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 collarbones
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Seven Letter Word Alert: (43 words)
aerosol, balloon, beacons, boleros, boolean, boranes, broncos, cablers, caboose, callers, callose, canoers, carbons, cellars, cloners, coalers, coarsen, collars, colonel, console, coolers, corneal, corneas, corolla, coronal, coronas, creosol, enrolls, escolar, lancers, loaners, locales, losable, ocellar, oracles, orleans, racoons, recalls, recoals, reloans, roseola, scleral, solacer