The word racehorse 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: 14
Highest Scoring Words With Friends™ Play In The Letters racehorse
:
Seven Letter Word Alert: (21 words)
acerose, archers, careers, coarser, coherer, coheres, crasher, creaser, echoers, hearers, hoarser, reacher, reaches, rearose, rechose, rehears, rescore, reshare, reshore, roaches, shearer