Which process is used by animals to remove ingested foods that cannot be digested?

Defecation

Explanation:

One of the functions of the digestive system is "defecation". The digested materials that were not absorbed through the small intestine leave the body through the anus and the process is called defecation. The eliminated material is called feces.  

Chyme enters the large intestine and remains there for about 3–10 hours. During this time, chyme is converted into solid or semisolid as most of the water is absorbed. It is now called feces. Feces consist of water, inorganic salts, some sloughed-off cells, bacteria, unabsorbed digested materials, and indigestible parts of food. Mass peristaltic movements push the fecal material from the sigmoid colon into the rectum. The defecation reflex that results in the elimination of feces from the rectum through the anus.