The word trilobites 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 trilobites
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Seven Letter Word Alert: (37 words)
betoils, biolite, biotest, biotite, bitsier, bitters, bittier, blister, blotter, boilers, bolster, bolters, bottler, bottles, bristle, bristol, brittle, elitist, estriol, iolites, litters, lobster, loiters, oiliest, reboils, retilts, riblets, risible, setbolt, siltier, slitter, sorbite, stilter, tilters, toilers, toilets, trilobe