[over one's head] {adv.}
or {adj. phr.}
1. Not understandable; beyond your ability to understand; too hard or strange for you to understand.
* /Mary laughed just to be polite, but the joke was really over her head./* /The lesson today was hard; it went over my head./
Compare: BEYOND ONE'S DEPTH. 2. To a more important person in charge; to a higher official.
* /When Mary's supervisor said no, Mary went over her head to the person in charge of the whole department./* /If Johnny can't get what he wants from his big sister, he goes over her head and asks his mother./
3. See: HANG OVER ONE'S HEAD.