1743, trans. Philip Francis, Horace Chapter Odes, My Grecians shall victorious prove, By me led on to War, the Sister-Wife of Jove.
1853, Henry N. Humphreys, The coin collector's manual, Ptolemy VII married Cleopatra the sister-wife of his predecessor.
1974, Joseph Fontenrose, Python: A Study of Delphic Myth and Its Origins‎, Anat as sister-wife of Baal, Isis as mother of Horos and sister-wife of Osiris, Hera as sister-wife of Zeus
In a polygamous marriage, a woman who is simultaneously the sister and co-wife of another.
1853, quoted in Robert Cox, Sabbath Laws and Sabbath Duties, Enmities between sister-wives will be, from their having known each other too intimately all their lives, more unmannerly than where they are strangers to each other
A co-wife in general.
2008, Miriam Koktvedgaard Zeitzen, Polygamy: A Cross-Cultural Analysis, The concept of 'sisterhood' was popularly applied to the official organizations for Mormon women, and Mormon co-wives were and are still known as 'sister-wives'
2006, Xiaoxiaosheng, trans. David Tod Roy, The plum in the golden vase, or, Chin P'ing Mei, Yüeh-niang and her sister-wives, all dressed in formal gowns, came out from inside to greet them and ushered them into the rear reception hall