As a Noun:
1. Something that is known about by only a small number of people, and is not told or shown to anyone else. English = secret.
2.
As a Verb or Adjective:
1. To be known about only by a small number of people and be kept that way by not being told or shown to anyone else. English = (be) secret, (be) confidential, (be) private.
2. To make something a secret, to make something confidential; to keep a secret, to keep someone's confidence.
3. To keep your knowledge, feelings, or intentions hidden from other people. English = (be) secretive.
Interactive:
1. Used alone, especially with extra stress, to tell your conversational partner to stop talking, particularly if they are about to reveal a secret. English = Shut up! Be quite! Idiomatic English = Don't spill the beans! Don't let the cat out of the bag.