The "dora" is a special tile worth extra points in the game of Japanese Mahjong. Specifically, it is the tile that is one higher than the "dora indicator". For example, if the indicator is "3 of circles", then the dora is "4 of circles". This is analogous to this card's effect.
The card appears to depict a "dead wall" in Japanese Mahjong with a single "dora indicator" tile flipped, although the position of the indicator is different from usual.