Noah Webster
Insincere
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.