verb

• (transitive) To harm the good reputation of (a person).
  "The candidate tried to discredit his opponent."
• (transitive) To cause (an idea or piece of evidence) to seem false or unreliable.
  "The evidence would tend to discredit such a theory."

noun

• (countable or uncountable) Discrediting or disbelieving.
  "Mr. Burton disbelieves it, and has brought sufficient reasons for his discredit of so improbable a story."
• (countable) A person or thing that causes harm to a reputation, as of a person, family, or institution.
  "[…] that now and then a young man of that profession did actually appear among us, who was not a discredit to his country."
• (uncountable) The state of being discredited or disbelieved.
  "Later accounts have brought the story into discredit."
• (uncountable) A degree of dishonour or disesteem; ill repute; reproach.
  "It is the duty of every Christian to be concerned for the reputation or discredit his life may bring on his profession."