Pronunciation: ( —n.dē'fekt, di-fekt'; —v.di-fekt'),[key] —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. Also called crystal defect, lattice defect.Crystall.a discontinuity in the lattice of a crystal caused by missing or extra atoms or ions, or by dislocations.
—v.i. 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.