刷 = to repeatedly do/farm something for drops or progress. The pattern is highly productive:
刷副本 (run dungeons),
刷怪 (kill mobs for drops),
刷经验 (grind XP),
刷金币 (grind gold),
刷成就 (achievement-hunt). Outside games,
刷 also means scroll:
刷抖音 (scroll TikTok).