What does this matrix notation mean?

Question

What does $|\textbf{M}|$ mean, where $\textbf{M}$ is a matrix? I am under the impression that you can element-wise divide $\textbf{M}$ by $|\textbf{M}|$ to normalize it in some way, kind of like how $|\textbf{v}|$, where $\textbf{v}$ is a vector, means the length of the vector, and by dividing these we get a unit vector.