The word matrilineal 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 matrilineal
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Seven Letter Word Alert: (41 words)
ailment, airline, airmail, airtime, aliment, alltime, amentia, animate, inertia, interim, laminae, laminal, laminar, lateral, latrine, limelit, limiter, lintier, literal, maltier, manilla, manlier, marital, marlite, martial, martian, martini, militar, minaret, mineral, miniate, mintier, netmail, raiment, ratline, reliant, retinal, tallier, termini, tramell, trenail