Having possession/ownership of one or more slaves. (adjective)
An owning of one or more slaves. (noun)
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Use "slaveholding" in a sentence
"Although the brutality of her fictional Maryland slaveholding is actually not as bad as the real Carolinas plantation described by Fanny Kemble a little later in time, it seems more shocking to have it witnessed by someone who is a contemporary of ours."
"For an interesting view of what these household dynamics meant in slaveholding society, see Stephanie McCurry,"
"Time and again, Bolívar compromised with Latin American slaveholding elites in order to secure their support, allowing slavery to continue."