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.
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.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.