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 chose between indulging your own deficiencies in this area or the car's.

Definitions of deficient

adj inadequate in amount or degree

“a deficient education”
deficient in common sense”
lacking, wanting
inadequate, unequal
lacking the requisite qualities or resources to meet a task

adj of a quantity not able to fulfill a need or requirement

meager, meagerly, meagre, scrimpy, stingy
deficient in amount or quality or extent
depleted, low
no longer sufficient
inadequate, poor, short
not sufficient to meet a need
lean, skimpy
containing little excess
light, scant, short
less than the correct or legal or full amount often deliberately so
of a quantity that can fulfill a need or requirement but without being abundant
more than enough in size or scope or capacity
adequate, decent, enough
sufficient for the purpose
sufficient to provide comfort
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adj falling short of some prescribed norm

inferior, substandard
varying from or not adhering to a standard

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