1. To put or to keep something or someone out of sight, or to prevent the person or thing from being found. "The evidence was carefully concealed by the prosecutor."
2. To keep something secret, or to prevent it from being known.
3. To hide; to withdraw, or to remove from observation; to cover or to keep from sight.
4. To prevent or to avoid disclosing or divulging something.

An attempt, whether successful or not, to conceal or to hide evidence of wrong-doing, some error, incompetence, or any other embarrassing information.