The word decrepitude 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: 20
Highest Scoring Words With Friends™ Plays In The Letters
Seven Letter Word Alert: (26 words)
creeped, cuprite, decider, decreed, decried, deducer, deepcut, deputed, detrude, epicure, erected, eructed, erudite, erupted, petered, picture, pierced, precede, predict, preedit, receded, receipt, recited, reduced, reputed, tepider