The word undergirding 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: 21
Highest Scoring Words With Friends™ Plays In The Letters undergirding
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Seven Letter Word Alert: (31 words)
dingier, dinging, drugged, druggie, dunging, giddier, girding, girning, gridder, grinded, grinder, grinned, grinner, grudged, grudger, guiding, gurning, inuring, nudging, regrind, reining, rending, ridding, ridging, ringing, ruddier, ruining, runnier, undined, undried, uridine