The word retrogressive 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: 19
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (67 words)
eeriest, egoists, erosive, erotise, goiters, goitres, goriest, greeter, griever, grieves, grister, grosser, grovers, grovets, oversee, overset, oversit, regives, regreet, regress, regrets, reserve, resorts, resters, restirs, restive, restore, retiree, retirer, retires, retrees, retries, reveres, reverie, reverse, reverts, reviser, revises, revotes, rioters, riveter, roister, rosiest, rosters, servers, severer, sievert, soirees, sorrier, sorters, sorties, steerer, stereos, stirrer, stivers, stogies, stories, striver, strives, terrier, terroir, terrors, tigress, verists, vertigo, vestige, vetoers