The word martingale 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 martingale
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Seven Letter Word Alert: (59 words)
agatine, ailment, aligner, aliment, amentia, animate, elating, garment, gateman, gelatin, geminal, genital, gmelina, granite, gremlin, ingrate, laminae, laminar, latrine, learing, magenta, magnate, maltier, malting, manager, mangier, mangler, manlier, margate, marital, marlite, martial, martian, melting, migrant, migrate, minaret, mineral, mingler, mintage, nametag, netmail, ragtime, raiment, ratline, realign, reaming, regalia, reliant, retinal, ringlet, tagline, tanager, tangier, tangram, teaming, tearing, tingler, trenail