Mid 19th century; earliest use found in Chambers's Journal of Popular Literature. Irregularly from climactic + -al, after e.g. syntactical, climacterical.
Definition of climactical in US English:
climactical
adjectiveklʌɪˈmaktɪkl
Climactic.
Origin
Mid 19th century; earliest use found in Chambers's Journal of Popular Literature. Irregularly from climactic + -al, after e.g. syntactical, climacterical.