1. Underdevelopment of a tissue or organ, usually due to a deficiency in the number of cells.
2. Atrophy due to destruction of some of the elements and not merely to their general reduction in size.
The information shown above for hypoplasia is provided by Stedman's.
* Stedman's, part of Lippincott Williams & Wilkins, provide a comprehensive line of health-science publications for healthcare professionals and medical students.