What does \[M\] mean in Maths?

Hint: Roman numerals are the symbolic representation of numbers in the ancient Roman system. They are represented by Latin symbols $I,V,X,L,C,D,M$.
The slope of a line gives us a measure of the steepness or the direction of the line. The slope can be easily calculated by taking the difference between the coordinates of any two points in the line.

Complete step-by-step answer:
There are different meanings in mathematics for \[M\] :
Firstly \[M\] is a Roman numeral. It is the symbolic representation of $1000$ in the Roman system. It is used to represent numbers in the Roman system starting with $1000$ by combining them with other symbols. The Roman numeral system is often required to convert numbers from the Hindu Arabic system.

Secondly, \[M\] represents the slope of a line in algebra. So the slope of a line $M$can be calculated using the formula $M = \dfrac{{\left( {{x_2} - {x_1}} \right)}}{{\left( {{y_2} - {y_1}} \right)}}$ where $\left( {{x_1},{y_1}} \right)$ and $\left( {{x_2},{y_2}} \right)$ are the coordinates of two points on the line.
The slope-intercept form of a line is given by the equation $y = mx + c$, where $m$ represents the slope of the line. We need to determine the slope of a line for various big problems in Mathematics.
So the use of $M$is widespread in Mathematics.

Note: One must not assume $M$ to be the mean, median, or mode of a dataset because they are not represented by this symbol. One should be well acquainted with Roman numerals to understand which number is represented by $M$. In algebra, the slope of a line is calculated all the time and there we can see the use of $M$ more often.