The word endocardium 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: 21
Highest Scoring Words With Friends™ Play In The Letters endocardium
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Seven Letter Word Alert: (54 words)
adducer, adenoid, admired, adorned, amidone, android, aneroid, arenium, cairned, candied, carmine, comrade, cranium, crunode, dandier, decidua, decorum, decuman, demonic, dermoid, diamond, dormice, drained, educand, enamour, incomer, induced, inducer, manured, marconi, moraine, mounded, mourned, muddier, neuroma, nomadic, numeric, radioed, redound, remound, roadmen, romaine, romance, rounded, unaided, unaimed, unaired, unarmed, uncared, uncoded, uncored, uncrime, undried, uraemic