A compound angle is an angle expressed in linear algebraic terms of other angles.
If x, y, z are measures of three separate angles then any linear combination of these would be a compound angle such as, y+7, x+y, z-x, x+y+z, 3x+y, 2z-x+10, etc. A compound angle is made up of any number of other measures separated by + or -. In other words, a compound angle has more than 1 component angle.