A semiangle is a shape that is halfway between a straight line and a right angle.
A semiangle is a kind of shape that is not too sharp or too round.
Examples:
A semiangle looks like a part of a circle.
The corner of the paper is a semiangle.
The semiangle is not as sharp as a right angle.
I drew a semiangle, but it doesn't look like a real shape!
The semiangle is not as round as a circle, but not as sharp as a right angle.
I made a semiangle with my fingers and it looks like a small part of a circle.