Half of an angle; an angle that is less than 180 degrees.
Semiangles are like the corners of a square or a triangle.
Examples:
The corner of the square is a semiangle.
A triangle has three semiangles.
The semiangle is smaller than the full angle.
The semiangle is like a little corner.
I can draw a semiangle with my fingers.
The semiangle is not as big as the full angle.