The Lesson
An straight angle is an angle of 180°. A straight angle is a half of a revolution.Dictionary Definition
The Oxford English Dictionary defines a straight angle as "an angle of 180°."Real Examples of Straight Angles
The angles below are all straight angles:What's in a Name?
A straight angle is called straight because it forms a straight line.Do a 180
A straight angle is half a revolution, it changes the direction to point the other way.The phrases "do a 180", "a complete 180" refers to someone who completely changes their mind or direction the other way.