The word relativistic 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: (71 words)
activer, actives, airiest, article, artiest, attires, cartels, castile, cattier, caviler, ciliate, citrate, clarets, clatter, clavier, clitter, cristae, eclairs, elastic, elicits, elitist, estival, ileitis, ilvaite, iratest, irisate, italics, laciest, laicise, latites, lattice, litters, raciest, rattles, realist, recital, retails, retilts, revisit, saltier, satiric, scalier, scarlet, scatter, siltier, slatier, slitter, starlet, starlit, startle, statice, stative, stilter, stivier, striate, tactile, tastier, tertial, tilters, titivil, travels, trisect, trivets, trivial, varices, velaric, veritas, vesical, viscera, vitiate, vittles