Define inclusion . inclusion synonyms, inclusion pronunciation, inclusion translation, English dictionary definition of inclusion . n. 1. The act of including or the state of being included. 2. Something included. 3. A solid, liquid, or gaseous foreign body enclosed in a mineral or rock.... INCLUSION definition : 1. the act of including someone or something as part of a group, list, etc., or a person or thing…. Learn more. What is Inclusion ? Learn the inclusion definition and the difference between inclusion and diversity in theory. The noun ' inclusion ' is derived from the Latin word 'inclusio,' which is a derivative of the verb 'includere.' 'Includere' is a combination of 'in' ( meaning 'in' or 'into') and 'claudere' ( meaning 'to close' or 'to shut'). In Latin, 'inclusio' referred to the act of closing in or enclosing. Over time, ' inclusion ' took on a more figurative meaning , representing the act or process of embracing and incorporating individuals of diverse backgrounds, identities, and abilities into a welcoming and ...