The word overconfidence 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: 30
Highest Scoring Words With Friends™ Play In The Letters overconfidence
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Seven Letter Word Alert: (41 words)
cervoid, codeine, codrive, codrove, coerced, concede, concern, concord, condone, confide, confine, conifer, connive, convene, cornice, covered, crevice, crooned, deceive, defence, definer, deforce, divorce, eccrine, encoder, encored, enforce, environ, evinced, fevered, inferno, needier, nonfeed, nonfire, nonfree, nonvoid, overfed, receive, refence, refined, revoice