The word underpants 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: 17
Highest Scoring Words With Friends™ Play In The Letters underpants
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Seven Letter Word Alert: (49 words)
asunder, departs, dustpan, entraps, natured, natures, panders, panters, parents, pasture, peanuts, pedants, pendant, petards, pretans, prudent, punners, punster, punters, saunter, spanned, spanner, spurned, spurted, stander, standup, stunned, stunner, suntrap, tanners, trepans, tundras, undents, undrape, undrest, unearnt, unparse, unrated, unsated, unspent, unstrap, untaped, untraps, untread, updater, updates, uprated, uprates, uptrend