noun Date: 1908 a card in stud poker that is properly dealt facedown and that the holder need not expose before the showdown, something (as a reliable advantage) that is held in reserve especially for use at a strategic moment
HOLE CARD
Meaning of HOLE CARD in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012