interpolation

n. [ L. interpolatio an alteration made here and there: cf. F. interpolation. ] 1. The act of introducing or inserting anything, especially that which is spurious or foreign. [ 1913 Webster ]

2. That which is introduced or inserted, especially something foreign or spurious. [ 1913 Webster ]

Bentley wrote a letter . . . . upon the scriptural glosses in our present copies of Hesychius, which he considered interpolations from a later hand. De Quincey. [ 1913 Webster ]

3. (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. [ 1913 Webster ]