de·pres·sion (dĭ-prĕshˈən)

1. The act of depressing or the state of being depressed.
2. A reduction in physiological vigor or activity.
3. A lowering in amount, degree, or position.
4. An inward displacement of a body part.
5. A hollow or sunken area.
6. The condition of feeling sad or despondent.
7. A psychiatric disorder characterized by an inability to concentrate, insomnia, loss of appetite, anhedonia, feelings of extreme sadness, guilt, helplessness and hopelessness, and thoughts of death. Also called clinical depression.