to mean B.S. or ,theres no way. Also to mean one having no fear
Your idea didn't work "Balls!it didn't." " It took balls to tell him off."
An exclamation used to describe either the positive, or negative extreme on the 'awesome scale'.
Or something both positive and negative simultaneously
Positive: "That scythe is so balls!"
Negative: "Aw, BALLS! My car ran out of gas!"
Both Simultaneously: "You kicked that ball from all the other side of the field and hit me in the face! That was balls!"