| APA | Smart Define. (2015). unheard-of thesaurus. Retrieved October 1, 2026, from https://smartdefine.org/unheard-of/thesaurus/antonyms |
| Chicago | Smart Define. 2015. "unheard-of thesaurus" https://smartdefine.org/unheard-of/thesaurus/antonyms (accessed October 1, 2026). |
| Harvard | Smart Define 2015, unheard-of thesaurus, Smart Define, viewed 1 October, 2026, <https://smartdefine.org/unheard-of/thesaurus/antonyms>. |
| MLA | Smart Define. "unheard-of thesaurus" 14 April 2015. Web. 1 October 2026. <https://smartdefine.org/unheard-of/thesaurus/antonyms> |