interpolation

from The Century Dictionary.

• noun The act of interpolating; the insertion of new words or expressions in a book or manuscript; especially, the falsification of a text by spurious or unauthorized insertions.
• noun That which is interpolated; new or (especially) spurious matter inserted; an unannounced or unauthorized insertion in a text.
• noun In mathematics, the process of finding, from the given values of a function for certain values of the variable, its approximate value for an intermediate value of the variable.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of introducing or inserting anything, especially that which is spurious or foreign.
• noun That which is introduced or inserted, especially something foreign or spurious.
• noun (Math.) The method or operation of finding from a few given terms of a series, as of numbers or observations, other intermediate terms in conformity with the law of the series.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun music An abrupt change in elements, with continuation of the first idea.
• noun mathematics, sciences the process of estimating the value of a function at a point from its values at nearby points.
• noun computing The process of including and processing externally-fetched data in a document or program; see interpolate.
• noun That which is introduced or inserted, especially something foreign or spurious.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a message (spoken or written) that is introduced or inserted
• noun (mathematics) calculation of the value of a function between the values already known
• noun the action of interjecting or interposing an action or remark that interrupts