The word breastbones 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: 18
Highest Scoring Words With Friends™ Play In The Letters breastbones
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Seven Letter Word Alert: (50 words)
abortee, absents, absorbs, atoners, banters, baronet, basters, beaters, berates, besorts, boaster, boaters, boneset, boranes, borates, boreens, breasts, earnest, eastern, enrobes, ensears, estrone, nearest, nesters, rabbets, reasons, rebases, rebates, reboast, renests, reseats, resents, roseate, sateens, seaters, senates, senator, sensate, sobbers, sorbate, sorbets, stabber, stenose, sterane, stereos, stoners, strobes, teasers, tensors, treason