up to one's eyeballs en · X
Etymology
See up to here.
Meanings
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Deeply engaged in something, to the point of being overwhelmed.
First and foremost (rather than last but not least), I couldn't have done this without my wife Nicki Norman, who serves as sounding board and a voice of rationality and moderation, and who sees the big picture when I'm up to my eyeballs in details.
2010, Peter H. Gleick, Bottled and Sold: The Story Behind Our Obsession with Bottled Water: