The word slaveholder 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: 20
Highest Scoring Words With Friends™ Play In The Letters slaveholder
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Seven Letter Word Alert: (48 words)
adheres, adverse, alveole, areoles, dealers, delvers, dollars, elodeas, evaders, halvers, headers, healder, healers, hearsed, heavers, heralds, holders, hollers, hoveled, hoveler, hovered, laveers, leaders, leashed, leavers, loaders, ordeals, overall, overled, oversea, raveled, redeals, reloads, resaved, reshave, reshoed, resoled, resolve, reveals, savored, several, sheared, sheaved, shelled, sheller, shelved, shelver, shoaled