A batsu, drawn as an "X", is the Japanese
symbol for "wrong" or "incorrect".
This is in opposition to maru
, drawn as "O", which is used to connote roundness and correctness. A sankaku
, or triangle-mark, is used as a sign of partial completion.
Sometimes, people play a batsu game
--in which if someone fails a dare or loses at jan ken pon
, that loser must suffer some penalty or do some embarassing act/favor.