illustre verb 2adjective 1forms 3 verb2 •(no longer used) To illuminate (something).But, as the Phoenix on my Front doth glister, / Thou shalt the Finials of my Frame illustre. — 1608 •(no longer used) To make (someone) illustrious. adjective1 •(no longer used) Synonym of illustrious. formsillustred · illustring · illustres