Antediluvian (an’te di loo ve an), adj 1.of or belonging to a period before the Flood. 2. harking back to an earlier time; out of date; antiquated: antediluvian ideas noun 3. a person who lived before the Flood. 4. a very old-fashioned  person or thing. 5. an old boys rugby player or team based out of Edmonton, Alberta with a world wide membership devoted to great old boys rugby on and off the field.