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1. A decrease, decline, or relaxation, as of effort or energy.
2. A disappointment: The cancellation of the game was a real letdown.
3. The descent made by an aircraft in order to land.
4. A physiological response in lactating females, activated usually in response to sucking or crying by an infant, in which milk previously secreted into the alveoli of the breasts is released into the ducts that lead to the nipple.

milk letdown

, letdown
The ejection of a mother's milk from the alveoli of the breast into the mammary ducts and to the nipple.


1. the sudden flush of milk flow that occurs when the calf begins to suck or when milking commences in a properly prepared cow. Depends for its occurrence on the release of oxytocin from the pituitary gland in response to massage of the teats and udder. Environmental stimuli such as free electricity and fear or excitement can block the response. Is also sometimes absent in freshly calved cows but the cycle can be triggered by an injection of oxytocin.
2. a horse in overfat condition is said to be letdown; the converse of tuckedup.

milk letdown failure
occurs sporadically in all species. May be due to painful conditions of the teat or sharp teeth of sucker. Anxiety, as in maiden heifers, can be a cause. Other cases occur without obvious reason and respond dramatically to a single injection of oxytocin.