Can anyone define "waste gate" for me?

what is it , how does it work , etc?

I need to settle an argument.

 

My turbo book says...."The wastegate derives it's name from the fact that it functions by wasting a portion of the exhaust energy. By wasting, or bypassing, a controlled amount of exhaust gas energy around the turbine, the actual speed of the turbine, hence the boost, can be controlled......It is nothing more than an exhaust gas bypass valve" by Corky Bell

Hope this helps
RJ