Idiom: to cross one's fingers; used as a verb
First Example:
Oscar: I have a job interview later today.
Tiffany: What's it for?
Oscar: A new startup - it pays better than my current job; plus, it's what I went to school for.
Tiffany: That sound perfect.
Oscar: Yeah. Cross your fingers that it goes well.
Tiffany: I will!
Meaning: The expression "to cross one's fingers " means to wish for something to happen. In the above example, Oscar says Tiffany to "cross your fingers" that his interview goes well. In American culture, people often physically cross their fingers to non-verbally say "wish me luck;" you can also ask someone to "cross their fingers" or say that you are "crossing your fingers" without physically doing so for the same meaning.
Second Example:
Mom: Why were you up all night?
Son: I was studying. I have a big test today.
Mom: I thought you were playing video games.
Son: No, I'm just nervous about this test.