deficient
Americanadjective
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lacking some element or characteristic; defective.
deficient in taste.
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insufficient; inadequate.
deficient knowledge.
noun
adjective
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lacking some essential; incomplete; defective
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inadequate in quantity or supply; insufficient
Other Word Forms
Etymology
Origin of deficient
First recorded in 1575–85; from Latin dēficient-, stem of dēficiēns “failing,” present participle of dēficere “to fail, run short, lack, weaken,” from dē- de- + ficere, combining form of facere “to do, make” ( see also do 1)
Explanation
Deficient means not enough or not adequate. Maybe you were deficient in caffeine that day. Maybe you were lacking in study time. But no doubt about it: you came up with a deficient number of correct answers on the physics test. If your new car fund remains deficient, you don't have enough money to buy a new car. This presents a problem if your current car is deficient in some way — say, it no longer has enough engine power to drive up a hill. You may not feel you have what it takes to get a job, but the reality is you will have to choose between indulging your own deficiencies in this area or the car's.
Vocabulary lists containing deficient
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The addition of heavy landscape planters and thick paving stone on the pool deck in the 1990s further stressed the building, adding tons of uncalculated deadweight to the deficient slab.
From The Wall Street Journal ● Jun. 22, 2026
Being truly deficient in B6 is rare, although sometimes levels can be a bit low, often alongside a lack of other B vitamins, such as B12, which can leave you feeling tired and nauseous.
From BBC ● Apr. 22, 2026
These provide calories but lack the sterols bees need, leaving colonies nutritionally deficient.
From Science Daily ● Mar. 27, 2026
Iran, which is an IMO member but does not sit on its council, hit out at the declaration, branding it "one-sided, unfair, inaccurate and legally deficient".
From Barron's ● Mar. 19, 2026
In the thirteen years since she’d left Moton High School, the deficient building had passed from being merely overcrowded to packed beyond reasonable measure.
From "Hidden Figures" by Margot Lee Shetterly
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
