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

Another furious attack towards the end of the round left Wardley in deep trouble.

From BBC ● Oct. 17, 2026

That creates a “unique window” to invest in deep tech that can support AI demand, said Gryseels, who previously led McKinsey’s technology and innovation practice.

From The Wall Street Journal ● Oct. 13, 2026

Japan undoubtedly has an edge in deep technology and entertainment content, Tomita said.

From The Wall Street Journal ● Oct. 1, 2026

There were no shops that she could see in the direction she had to walk, only dull mansion blocks of flats in deep orange brick.

From "Atonement" by Ian McEwan

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