<p><strong>Noun</strong></p><ul><li>a shortcoming, fault, or imperfection: a defect in a machine.</li><li>a defect in an argument; a defect in a machine.</li><li>lack or want, especially of something essential to perfection or completeness; deficiency: a defect of action.</li><li>a defect of common sense.</li><li>a defect of action.</li><li>also called crystal defect, crystallography: a discontinuity in the lattice of a crystal caused by missing or extra atoms or ions, or by dislocations.</li></ul><p><strong>Verb</strong></p><ul><li>(used without object) to desert a cause, country, etc., especially in order to adopt another (often followed by from or to): He defected from the U.S.S.R. to the West.</li></ul>