The word billionaires 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™ Plays In The Letters billionaires
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Seven Letter Word Alert: (31 words)
aileron, airline, albinos, alibies, billion, boilers, boranes, braille, elision, enrolls, ioniser, ironies, lesbian, liaison, liberal, lionise, loaners, lobelia, losable, nailers, noisier, orleans, rallies, rebills, reboils, reloans, renails, risible, sealion, sillier, sirloin