An expression is said to be ambiguous (or poorly defined) if its definition does not assign it a unique interpretation or value. An expression which is not ambiguous is said to be well-defined.
Ambiguous
See also
Ill-Defined, Well-DefinedExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Ambiguous." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Ambiguous.html