over one's head

1. To a position higher than another's, as in She was furious when her assistant was promoted over her head . Similarly, go over someone's head means “appeal to a higher authority,” as in Since she couldn't help me, I decided to go over her head and talk to her supervisor . [Mid-1500s]

2. Beyond one's understanding or competence, as in The math required to complete these figures is way over my head . [Early 1600s] For a synonym, see out of one's depth . Also see in deep (over one's head) .