\documentclass{article}
\usepackage{unicode-math}
\newcommand\closure[1]{\overline{#1}}
\begin{document}
The intersection of the closed ball $\overline{B}(1)$ with the closed
ball $\closure{B}(2)$ is the same as the intersection of the closed
ball $\closure{B}(2)$ with the closed ball $\overline{B}(1)$.
\end{document}
Further details
unicode-math silently overrides the user defined command.
Description
unicode-math-tablehas\UnicodeMathSymbol{"02050}{\closure}{\mathrel}{close up}which doesn't seem semantically correct.Check/indicate
Minimal example demonstrating the issue
Further details
unicode-mathsilently overrides the user defined command.