底牌

cards in one's hand / (fig.) undisclosed strength or information / hidden trump

(equivalent to 的 as possessive particle)

background / bottom / base / end (of the month, year etc) / remnants / (math.) radix / base

mahjong tile / playing card / game pieces / signboard / plate / tablet / medal / CL:片[pian4],個|个[ge4],塊|块[kuai4]

to show one's hand / to lay one's cards on the table