INSINCE'RE, adjective [Latin insincerus; in and sincerus, sincere.] 1. Not sincere; not being in truth what one appears to be; dissembling; hypocritical; false; used of persons; as an insincere heart. 2. Deceitful; hypocritical; false; used of things; as insincere declarations or professions. 3. Not sound.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI