godan verb (-ru), intransitive verb
do earnestly; get serious; go all out
Slang verb formed from ガチ (serious, real) + る. Used mainly in casual speech among younger speakers to mean doing something seriously, earnestly, or going all out. Often implies a competitive or committed attitude.
See also: ガチ
次の試合はガチって勝ちに行く。
I'll get serious and go for the win in the next match.
彼はゲームになるとすぐガチる。
He gets serious as soon as it comes to games.