The word countersunk 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: 22
Highest Scoring Words With Friends™ Play In The Letters countersunk
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Seven Letter Word Alert: (31 words)
conkers, consent, cornets, counter, couture, encrust, nektons, neurons, neutron, noncute, nonuser, outruns, reckons, recount, reknots, restock, restuck, rockets, scouter, stocker, stunner, tenuous, tonsure, trounce, tuckers, uncorks, uncurse, unknots, unstock, unstuck, untucks