An alternative to saying "good man". This word was born from saying "good man" multiple times in quick succession, usually 3 times. It is pronounced "mang-an-ah", not "man-ghana".
It is also good practise to repeat it using an echo style effect until it becomes inaudible.
Pete: This week I scored not only with one chick but two.
Stu: Mangana! Mangana! Mangana! Mangana!