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WordNet
lactiferous duct

n. ducts of the mammary gland that carry milk to the nipple

Wikipedia
Lactiferous duct

Lactiferous ducts form a tree branched system connecting the lobules of the mammary gland to the tip of the nipple. They are also referred to as galactophores, galactophorous ducts, mammary ducts, mamillary ducts and milk ducts. They are the structures which carry milk toward the nipple in a lactating female.