A minimization of the maximum error for a fixed number of terms.
Minimax Approximation
See also
Remez Algorithm, Minimax Polynomial, Minimax TheoremExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Minimax Approximation." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/MinimaxApproximation.html