In Statistics & Probability, a peak refers to a high point or 'bump' in a set of data.
It is often associated with the mode - the most common data value.
Example
The peak number of matches is 50.
This is the same as the mode.
A peak can sometimes refer to the maximum point on a graph. These are most often called maximum turning points.
Example
The parabola below has a peak (maximum turning point) at (2, 4).