- cross\ one's\ fingers
- v. phr.1a. To cross two fingers of one hand for good luck.11b. or keep one's fingers crossed
Mary crossed her fingers during the race so that Tom would win.
informalTo wish for good luck.Keep your fingers crossed while I take the test.
2. To cross two fingers of one hand to excuse an untruth that you are telling.Johnny crossed his fingers when he told his mother the lie.
Словарь американских идиом. — СПб., Изд-во "Лань". Оригинал: A.Маккей, М.Т.Боткер, Дж.И.Гейтс. 1997.