talk over head
talk over (one's) head
To talk about things that one cannot follow, understand, or comprehend. Your presentation shouldn't focus on the technical details too much; you don't want to talk over everyone's heads. I hate the way he always tries to talk over my head, as if I'm too dumb to understand what he's talking about.
talk over someone's head
Fig. to say things that someone cannot understand; to speak on too high a level for one's audience. The speaker talked over our heads and we learned nothing. It is not a good idea to talk over your audience's heads.