摊牌 is a separable verb (离合词) that literally means 'to spread out one's cards' — a poker metaphor. In everyday use it means to reveal your true intentions or position, forcing a final decision or confrontation. The verb 摊 can separate from the noun 牌 when you insert aspect markers, durations, or objects: 摊了牌 ('showed one's hand'), 摊什么牌 ('what cards are you showing'). You'll hear it in negotiations, conflicts, or any situation where someone stops hiding their real stance.