1.VerbTo put the middle finger across the index finger, especially:
"She was seen crossing her fingers in the wedding photo.; I hope everything turns out OK. I'll cross my fingers for you. / I'll cross my fingers that everything turns out OK."
2.Verbwhen wishing for luck, or
"I hope everything turns out OK. I'll cross my fingers for you. / I'll cross my fingers that everything turns out OK."
3.Verbwhen telling a lie (and attempting to escape the moral and other consequence of that lie).