The word fleetingness 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: (51 words)
elegies, elegise, elegist, elegits, engines, enlists, ensigns, feeling, feesing, felines, felsite, felting, fennels, finesse, finless, fitness, fleeing, flenses, geneses, genesis, gentile, gentles, glisten, infests, ingests, intense, lefties, lenient, lenites, lensing, linnets, listens, nesting, nestles, netless, seitens, selfies, sensing, sestine, signees, signets, silents, singles, singlet, steelie, stifles, tensile, tensing, tieless, tingles, tinsels