verb

• (transitive) To forgive; to pardon; to overlook.
  "I excused him his transgressions."
• (transitive) To allow to leave, or release from any obligation.
  "May I be excused from the table?"
• (transitive) To provide an excuse for; to justify.
  "You know he shouldn't have done it, so don't try to excuse his behavior!"

noun

• (countable, uncountable) An explanation designed to avoid or alleviate guilt or negative judgment; a plea offered in extenuation of a fault.
  "Tell me why you were late – and I don't want to hear any excuses!"
• (law) A defense to a criminal or civil charge wherein the accused party admits to doing acts for which legal consequences would normally be appropriate, but asserts that special circumstances relieve that party of culpability for having done those acts.
• (often with preceding negative adjective, especially sorry, poor, or lame) An example of something that is substandard or of inferior quality.
  "That thing is a poor excuse for a gingerbread man. Hasn't anyone taught you how to bake?"