What is the meaning of interpolation?

noun

• A message (spoken or written) that is introduced or inserted.
  • usage: "with the help of his friend's interpolations his story was eventually told"; "with many insertions in the margins"
  • synonyms: insertion
• Mathematics) calculation of the value of a function between the values already known. (
• The action of interjecting or interposing an action or remark that interrupts.
  • synonyms: interjection, interposition, interpellation