The word flabbergast 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™ Plays In The Letters flabbergast
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Seven Letter Word Alert: (26 words)
abaters, ablates, abreast, algebra, arblast, barbels, belfast, blaster, eartags, falters, fatberg, fleabag, gabbers, gabbler, gabbles, garbles, grabble, laagers, largest, rabbets, reblast, reflags, stabber, stabler, teabags, teargas