expression, godan verb (-u)
beat someone at their own game; outdo someone in their specialty
Idiomatic expression used when someone surpasses another person in the very area that person is known for or prides themselves on.
彼は料理自慢の友人をお株を奪うような腕前で驚かせた。
He surprised his friend who prides himself on cooking with skills that beat him at his own game.
The newcomer gave a presentation that outdid the veteran employee in his own specialty.