The word gigahertzes 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: 26
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (27 words)
aeriest, aigrets, atheise, atheize, eggiest, eighter, gaiters, gathers, gearset, hastier, haziest, heaters, hertzes, reheats, resight, restage, saggier, seriate, sighter, stagger, stagier, taggees, taggers, taggier, triages, zestier, zithers