Lactate/ˈlækteɪt/ Definition 1 of 3Pro Tip 1/3Biology Context Used when discussing the biology of mammals, referring to milk production. The newly born puppy needs its mother to lactate to survive. Pro Tip 2/3Not Just Humans Understand lactating applies to all female mammals, not exclusively humans. In the wild, a lioness will lactate to feed her cubs. Pro Tip 3/3Mammalian Trait It's a distinctive characteristic of mammals, setting them apart from other animals. One feature that defines mammals is their ability to lactate.