over one's head
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]
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).
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