A basis, form, function, etc., in two or more variables is said to be multilinear if it is linear in each variable separately.
Multilinear
See also
Bilinear Function, Linear Operator, Multilinear Basis, Multilinear FormExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Multilinear." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Multilinear.html