That line is called a "Diameter".
diameter
great circle
It is called a great circle. The equator is an example.
equator
The Equator...
prime merideane and equator The equator divides the earth into two equal halves.
equator
an equator
You are drawing a line which divides the angle into 2 equal parts (halves).
A line segment that divides a circle in two is a chord.If the two parts of the circle are equal, the line segment is a diameter.See 'The Parts of the Circle' in Sources and related links, below.
A line passing through the center and crossing the circle.
A bisector is a line or curve which bisects or divides a line segment, angle or other figure into two equal parts.