|informal a person, institution, custom, etc, unreasonably held to be beyond criticism|
|[alluding to the Hindu belief that cattle are sacred]|
|the offspring of a zebra and a donkey.|
|an extraordinary or unusual thing, person, or event; an exceptional example or instance.|
Figuratively, anything that is beyond criticism: “That housing project is a real sacred cow: the city council won't hear of abandoning it.” In India, followers of Hinduism consider cows sacred and do not eat them because they believe the animals contain the souls of dead persons.