1. The consumption of a substance by an organism. In animals, it normally is accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms, ingestion can take place through taking the substance through the cell membrane. (wikipedia.org)
2. The action of ingesting, or consuming something orally, whether it be food, drink, medicine, or other substance. It is usually referred to as the first step of digestion. (wiktionary.org)
3. To take into the body by the mouth for digestion or absorption. (thefreedictionary.com)
4. To take in and absorb as food. (thefreedictionary.com)
5. The process or act of engulfing particles by cells (e.g. phagocytic cell). (biology-online.org)
Word origin: From Latin ingestionem “a pouring in,” noun of action from past participle stem of ingerere.