A right angle triangle perhaps
A segment from the vertex of a triangle perpendicular to the line containing the opposite side
line segment
median
Altitude
side
perpendicular
Altitude.
A line segment that connects a vertex of a triangle to a point on the line containing the opposite side, where the segment is perpendicular to that line, is known as an altitude of the triangle. This segment represents the shortest distance from the vertex to the opposite side, and it helps to determine the triangle's height when calculating its area. Each triangle has three altitudes, one from each vertex.
Altitude
Altitude
The description given fits that of a right angle triangle
altitude