(of a set of points) Not lying on a straight line.
(of a molecule) Whose atoms do not lie in a straight line.
(of a function) Having a product of independent variables, or a variable with an exponent not equal to one.
(of a system) Whose output is not directly proportional to its input.
Erratic and unpredictable; tending to jump back and forth.
a film with a nonlinear plot