To have triumphed in a battle that was reduced to matter of testicular fortitude. To produce a bollock of greater volume when confronted with an adversary of supposed superior masculinity.
While it is mainly used to describe events occurring in a sporting field of play, it would not be out of place when describing events in a theatre of war, a dance off or a game of scrabble.
Gambler 1: did you hear about Rafael Nadal yesterday?
Gambler 2: huh!? no i didnt man, what happened?
Gambler 1: Croat dude named Ivan Dodig beat him in 3 at Montreal Masters.
Gambler 2: hahahah bull**** man you're taking the mick
Gambler 1: no joke bro, Nadal was up 5-3 serving in the 3rd set, but nadal didn't choke... Dodig totally outbollocksed him.