刷 (literally 'to brush') is gamer jargon for 'farm / repeatedly do' - also in
刷怪 (grind mobs),
刷装备 (farm gear),
刷副本 (run dungeons),
刷金币 (farm gold),
刷经验 (grind XP). The verb implies repetitive grind.
副本 literally means 'duplicate/copy' - a per-party instance of the dungeon, hence the MMO 'instance' term.
