Altersdiskriminierung, d.h. Vorurteile gegenüber oder Diskriminierung von Menschen aufgrund ihres Alters.

1969
Dr. Robert Butler […] believes many of his Chevy Chase neighbors suffer from ‘age-ism’
Washington Post 7. März 1969, S. 6.

1969
we may soon have to consider very seriously a form of bigotry we now tend to overlook: age discrimination or age-ism, prejudice by one age group toward other age groups. If such bias exists, might it not be especially evident in America; a society that has traditionally valued pragmatism, action, power, and the vigor of youth over contemplation, reflection, experience, and the wisdom of age? […] Age-ism describes the subjective experience implied in the popular notion of the generation gap. Prejudice of the middle-aged against the old in this instance, and against the young in others, is a serious national problem. Age-ism reflects a deep seated uneasiness on the part of the young and middle-aged—a personal revulsion to and distaste for growing old, disease, disability; and fear of powerlessness, “uselessness,” and death. […]
Age-ism might parallel (it might be wishful thinking to say replace) racism as the great issue of the next 20 to 30 years
Robert N. Butler: Age-Ism: another form of bigotry, in: The Gerontologist 9 (1969), S. 243-246, hier S. 243; 246.

1970
At the recent International Congress on Gerontology in Washington, D.C., Prof. Bernice Neugarten of the University of Chicago’s Committee on Human Development had some important things to say which I would like to mention briefly. She points out that certain antagonisms toward the old may be forming which were not present before. [“]As the number of old people increases, the phenomenon that has been called “age-ism” may be directed toward the old just as it is presently being directed toward the young. Age-ism toward the old now takes many covert forms.[“] Professor Neugarten continues: [“]As witnessed by the pervasive pattern of attitudes that make us slow in providing meaningful roles for older people and in raising their status as an age–group; by the small percent of the welfare dollar that is spent for services to the aged; and even by the fact that research on aging is so slow to develop in both the biological and the social sciences.[“] Dr. Neugarten goes on to warn that: [“]It is possible that age-ism may take more overt forms in the near future… future generations of old will be different from our present old … they may become a more vocal and demanding group.[“] She concludes by pointing out that: [“]Attitudes toward age, the effects upon society of changing age distributions, the transmission of values across generations, changing age norms, and the relations between age groups should now become a central area of inquiry … for all social scientists.[“]
W.W. Morris [Iowa Commission on Aging]: [Statement], in: Older Americans in Rural Areas. Hearings before the Special Committee on Aging, United States Senate, Ninety-First Congress, First Session, part 1, Des Moines, Iowa, September 8, 1969, Washington 1970, S. 12-16, hier S. 15.

1971
the conflict of generations, or the study of the aged as an out-group or sub-culture, reflecting the growth of what Bernice Neugarten, Robert M. Butler, M.D., and others have called “age-ism,” and the roles of the aged in the political arena
Ethel Shanas: The sociology of aging and the aged, in: The Sociological Quarterly 12 (1971), S. 159-176, hier S. 173.

2020
ageism (engl.), in Analogie zu Rassismus, Sexismus usw. gebildet, bezeichnet die Diskriminierung von Menschen aufgrund ihres Alters sowie Vorstellungen die solche Diskriminierung befördern (etwa dass alte Menschen allgemein weniger leistungsfähig seien als junge).
Werner Fuchs-Heinritz: [Art.] ageism, in: Daniela Klimke et al. (Hg.): Lexikon zur Soziologie, 6. Aufl. Wiesbaden 2020, S. 10.