1. The process of removing water from a substance or compound.
2. The process of removing water from a food product in order to preserve it or to make it more portable.
3. Excessive loss of water from the body or from an organ or body part, as a result of illness or fluid deprivation.

A condition in which there is an excessive loss of water from the body tissues, caused by such factors as prolonged diarrhea or fever, repeated vomiting, and excessive perspiration or urination. Extreme dehydration may lead to shock or even death.