delusory de·lu·sory UK/dɪˈluːzəɹi/ uncommon adjective 1. causing one to believe what is not true or fail to believe what is true “deceptive calm” “a delusory pleasure” Synonymsdeceptive Similarunreal WordNet 2.1 (Princeton University). Wiktionary (CC BY-SA). WordNet 2.1 Copyright Princeton University. All rights reserved.