Mid 17th century. From post-classical Latin rationativus that expresses a reason from rationat-, past participial stem of rationari + classical Latin -īvus.
Definition of rationative in US English:
rationative
adjective
That involves ratiocination.
Origin
Mid 17th century. From post-classical Latin rationativus that expresses a reason from rationat-, past participial stem of rationari + classical Latin -īvus.