defect

UK: noun: /ˈdiːfɛkt/, verb: /dɪˈfɛkt/

US: /n. ˈdifɛkt, dɪˈfɛkt; v. dɪˈfɛkt/

US: (n. dē′fekt, di fekt′; v. di fekt′)

WordReference Random House Learner's Dictionary of American English © 2025

de•fect /n. ˈdifɛkt, dɪˈfɛkt; v. dɪˈfɛkt/   n. [countable]

1. a fault or shortcoming;
   imperfection:
   What defect in his character made him lie?

v. [no obj]

2. to desert a cause, country, etc., and go over to the opponent's side:
   Would the spies want to defect to the West?

de•fec•tion, n. 

[uncountable] the defection of several members of the ambassador's staff.

[countable] Defections increased during the crisis.

See -fec-.

WordReference Random House Unabridged Dictionary of American English © 2025

de•fect  (n. dē′fekt, di fekt′;v. di fekt′), n. 

1. a shortcoming, fault, or imperfection:
   a defect in an argument; a defect in a machine.
2. lack or want, esp. of something essential to perfection or completeness;
   deficiency:
   a defect in hearing.
3. Crystallography Also called crystal defect, lattice defect. a discontinuity in the lattice of a crystal caused by missing or extra atoms or ions, or by dislocations.

v.i. 

4. to desert a cause, country, etc., esp. in order to adopt another (often fol. by from or to):
   He defected from the U.S.S.R to the West.

• Latin dēfectus failure, weakness, equivalent. to dēfec- variant stem of dēficere to run short, fail, weaken (see deficient) + -tus suffix of verb, verbal action
• late Middle English 1375–1425

de•fect′i•ble, adj. 
de•fect′i•bil′i•ty, n. 
de•fect′less, adj. 
Synonyms

• 1. Defect, blemish, flaw refer to faults that detract from perfection.
  Defect is the general word for any kind of shortcoming or imperfection, whether literal or figurative:
  a defect in eyesight, in a plan.
  A blemish is usually a defect on a surface, which mars the appearance:
  a blemish on her cheek.
  Flaw is applied to a defect in quality, caused by imperfect structure (as in a diamond) or brought about during manufacture (as in texture of cloth, in clearness of glass, etc.).

Collins Concise English Dictionary © HarperCollins Publishers::

defect noun / dɪˈfɛkt ˈdiːfɛkt/

1. a lack of something necessary for completeness or perfection; shortcoming; deficiency
2. an imperfection, failing, or blemish

verb / dɪˈfɛkt/

1. (intransitive) to desert one's country, cause, allegiance, etc, esp in order to join the opposing forces

Etymology: 15th Century: from Latin dēfectus, from dēficere to forsake, fail; see deficient

deˈfector noun