The word nightriders 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: 17
Highest Scoring Words With Friends™ Play In The Letters nightriders
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Seven Letter Word Alert: (48 words)
dieting, dingier, dingies, dirtier, dirties, dishing, dithers, ditsier, editing, girders, girners, grinder, grister, herding, herring, hidings, hinders, ignited, igniter, ignites, inditer, indites, inherit, insider, insight, nightie, nitride, regrind, resight, resting, ridings, righted, righter, ringers, shindig, shinier, shirted, shrined, sighted, sighter, stinger, stirred, strider, tidiers, tidings, tiering, tigrish, tinders