The word irrelevant 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: 16
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (36 words)
alerter, arenite, averter, earlier, elative, enteral, eternal, inerter, latrine, learner, lineate, nervier, ratline, realter, reinter, relater, relearn, reliant, retinal, retrain, retrial, reviler, riveter, tearier, terrain, terrane, trailer, trainee, trainer, trenail, triaene, veinlet, veneral, ventral, veteran, vinelet