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"secrete milk from the breasts," 1889, probably a back-formation from lactation. Related: Lactated; lactating.
1794, from stem of lactic + -ate (1).
lactate lac·tate1 (lāk'tāt')v. lac·tat·ed, lac·tat·ing, lac·tates To secrete or produce milk.
lactate 2n. A salt or an ester of lactic acid.