The word gruesomeness 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: (26 words)
emerges, emerses, engross, ensures, geneses, genomes, genuses, grosses, grouses, guesser, guesses, mongers, morgues, mousers, mousses, mungers, negroes, reneges, renegue, resumes, ruesome, sensors, sermons, surgeon, unmerge, urnmoss