ˌtrade ˈsecret BrE AmE noun [countable]
1 . a piece of secret information about a particular business, that is only known by the people who work there:
The Coca-Cola formula is a well-kept trade secret.
2 . informal a piece of information about how to do or make something, that you do not want other people to know:
Could you give me the recipe for that ‘coq au vin’ or is it a trade secret?