The word postdiluvian 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: 23
Highest Scoring Words With Friends™ Play In The Letters postdiluvian
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Seven Letter Word Alert: (46 words)
astound, daltons, dialups, diptail, dopants, dualist, dustpan, idolist, inuloid, invalid, liaison, nuptial, outplan, outsail, outspan, outspin, pianist, pinitol, pintail, pivotal, plastid, plaudit, plutons, poundal, pundits, sandpit, slipout, spinout, spionid, standup, stipula, sundial, tailpin, talonid, topsail, unipods, unloads, unsplit, uplands, uploads, upsilon, upslant, utopian, utopias, violins, violist