The word registrant 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: 13
Highest Scoring Words With Friends™ Plays In The Letters
Seven Letter Word Alert: (76 words)
aigrets, angrier, antsier, argents, artiest, artsier, attirer, attires, earring, erasing, errants, gainers, gaiters, garners, garnets, garrets, garters, gastrin, girners, grainer, granite, granter, graters, grister, gritter, ingrate, instate, iratest, nastier, natters, nattier, nitrate, rangers, rangier, ranters, ratings, ratters, rattier, ratting, rearing, regains, regrant, restain, restart, resting, retains, retinas, retints, retrain, ringers, searing, seating, setting, stagier, stainer, staring, starter, stating, stinger, straint, strange, striate, tangier, targets, tarries, tarring, tastier, tasting, tearing, teasing, terrain, testing, tinters, trainer, transit, triages