The word undersides 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: 14
Highest Scoring Words With Friends™ Plays In The Letters undersides
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Seven Letter Word Alert: (29 words)
deniers, denuder, denudes, derides, desired, desires, disused, dresden, dressed, endured, endures, ensured, ensures, insured, insures, reddens, redness, reissue, resends, resided, resides, residue, ruddies, senders, suddens, sudsier, sunrise, undress, undried