age·ism also ag·ism (??j?z??m)n. Discrimination based on age, especially prejudice against the elderly.age?ist adj. & n.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.ageism (?e?d??z?m) or agismn (Sociology) discrimination against people on the grounds of age; specifically, discrimination against the elderly ?ageist, ?agist adjCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014age?ism (?e? d??z ?m) n. discrimination or prejudice against older persons. [1965?70] age?ist, adj., n. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.ageism, agismdiscrimination on the basis of age, especially against older people.See also: Age, Discrimination-Ologies & -Isms. Copyright 2008 The Gale Group, Inc. All rights reserved.