interlineation

The act of interlining; alteration or correction, as of written or printed matter, by interlinear insertion; also, that which is interlined; specifically, in law, an alteration made in a written instrument by inserting any matter after it is engrossed.

The act of interlining.

That which is interlined; a passage, word, or line inserted between lines already written or printed.

A notation made between the lines, especially in a handwritten document