1. The deliberate hiding, non-disclosure, or suppression of essential facts or circumstances that someone is legally or morally required to reveal; especially, with the intention to deceive or to defraud a person in a contractual arrangement.
2. Concealment, destruction or withholding of, or refusal to give, material evidence which a person has or knows and is legally or morally boung to reveal.

It is normally considered an '"obstruction of justice" which is a criminal offense.

3. A deliberate attempt to withhold information or to conceal an act to avoid a contractual responsibility.

Fraudulent concealment that is applied to health care providers comes up when a treating doctor conceals from an aggrieved patient that a previous treating doctor may have committed malpractice.