noun
Mathematical term for estimating values beyond a known range. Often contrasted with 補間法 (interpolation).
See also: 補間法
補外法を用いて将来の人口を推定した。
We estimated the future population using extrapolation.
Compound of 補 (supplement) + 外 (outside) + 法 (method), literally 'method of supplementing outside'. The exact derivation is uncertain; it is a technical term in mathematics.