The word antepenultimate 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: 25
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (65 words)
ailment, alanine, aliment, alumina, alumnae, amentia, amputee, animate, annulet, apatite, attelet, attempt, element, emanate, eminent, empanel, emplane, emulant, emulate, enamine, entente, entitle, epaulet, impanel, implant, laminae, lenient, lineate, lineman, linemen, maleate, manatee, matinee, meatpie, melanin, naptime, netmail, nuptial, nutmeal, nutmeat, paenula, paleate, palette, palmate, patient, patinae, peltate, penlite, penname, pentail, pentane, pentene, petunia, pinenut, pinnate, pinnule, planeta, plateau, putamen, tapeman, tapemen, teatime, umpteen, uneaten, unmeant