The word kilohertzes 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: 27
Highest Scoring Words With Friends™ Play In The Letters kilohertzes
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Seven Letter Word Alert: (30 words)
erotise, erotize, estriol, heroise, heroize, hertzes, heteros, holiest, holster, hostile, hostler, kestrel, kilters, kirtles, loiters, restoke, retiles, roselet, seltzer, shelter, skelter, slither, sterile, toelike, toilers, zeolite, zeroeth, zeroise, zestier, zithers