Meaning of SPLINE in English

[spline] n [origin unknown] (1756) 1: a thin wood or metal strip used in building construction

2: a key that is fixed to one of two connected mechanical parts and fits into a keyway in the other; also: a keyway for such a key

3: a function that is defined on an interval, is used to approximate a given function, and is composed of pieces of simple functions defined on subintervals and joined at their endpoints with a suitable degree of smoothness

Merriam-Webster English vocab.      Английский словарь Merriam Webster.