in deep

Idioms  

1. Seriously involved; far advanced. For example, He was in deep with the other merchants and couldn't strike out on his own , or She used her credit cards for everything, and before long she was in deep .

2. in deep water . Also, in over one's head . In trouble, with more difficulties than one can manage, as in The business was in deep water after the president resigned , or I'm afraid Bill got in over his head . These metaphoric expressions transfer the difficulties of being submerged to other problems. The first appears in Miles Coverdale's 1535 translation of the Book of Psalms (68:13): “I am come into deep waters.” The second, which also can signify being involved with more than one can understand, dates from the 1600s. Also see over one's head .

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Example Sentences

See Examples For:

in deep

Dr. Mayberg, Dr. Kopell, and Dr. Choi are named co-inventors on a patent application covering a technique for identifying optimal electrode placement in deep brain stimulation for depression.

From Science Daily ● Oct. 18, 2026

A venture-capital firm specializing in deep tech has raised more than $50 million to invest in startups that can help solve physical bottlenecks in artificial intelligence.

From The Wall Street Journal ● Oct. 13, 2026

It added that 11% of Scotland's overall population was defined as being in deep poverty and 7% in very deep poverty.

From BBC ● Oct. 5, 2026

Their size varies dramatically, from less than a centimeter long to more than 70 cm in Antarctica, where some species hunt smaller animals in deep ocean environments.

From Science Daily ● Sep. 25, 2026

She breathed in deep and, despite the unfamiliar clothes, could still smell her mother’s scent, shea butter lotion and a hint of pencil lead.

From "Ivy Aberdeen’s Letter to the World" by Ashley Herring Blake

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