1a. The act or process of assimilating. b. The state of being assimilated. 2.Physiology The conversion of nutriments into living tissue; constructive metabolism. 3.Linguistics The process by which a sound is modified so that it becomes similar or identical to an adjacent or nearby sound. For example, the prefix in- becomes im- in impossible by assimilation to the labial p of possible.4. The process whereby a minority group gradually adopts the customs and attitudes of the prevailing culture.