an imperfection in a crystal's lattice structure, either a missing atom or ion creating a vacancy in the lattice or an extra atom or ion between two normal lattice points creating an interstitial.
Examples from the web for point defect
If a point defect exists, the symmetry is broken, and the parameter will be a larger positive value.
point defect dynamics in two-dimensional colloidal crystals.
We review our understanding of the basic mechanisms active in such structures that can result in point defect generation.
British Dictionary definitions for point defect
point defect
noun
1.
an imperfection in a crystal, characterized by one unoccupied lattice position or one interstitial atom, molecule, or ion