Wikipedia: Ableism (/ˈeɪbəlɪzəm/; also known as ablism, disablism, anapirophobia, anapirism, and disability discrimination) is discrimination and social prejudice against people with disabilities or who are perceived to have disabilities. Ableism characterizes persons as defined by their disabilities and as inferior to the non-disabled. On this basis, people are assigned or denied certain perceived abilities, skills, or character orientations.
StopAbleism.org: The practices and dominant attitudes in society that devalue and limit the potential of persons with disabilities. A set of practices and beliefs that assign inferior value (worth) to people who have developmental, emotional, physical or psychiatric disabilities.
Anti-Oppression Guide: Ableism is prejudice plus power; anyone of any degree of physical or non-physical ability can have/exhibit ability-based prejudice, but in North America (and globally), societally enabled or nondisabled people have the institutional power, therefore Ableism is a systematized discrimination, antagonism, or exclusion directed against disabled people based on the belief that ‘normal ability’ is superior. Ableism involves both denying access to disabled people and exclusive attitudes of nondisabled persons. An ableist society is said to be one that treats nondisabled individuals as the standard of‘normal living’, which results in public and private places and services, education, and social work that are built to serve 'standard' people, thereby inherently excluding those with various disabilities.