unreasonal
/(ˌ)ʌnˈriːz(ə)n(ə)l/ /(ˌ)ʌnˈriːz(ə)n(ə)l/Now rare (chiefly US in later use)
adjective
Not reasonable.
Origin
Mid 17th century; earliest use found in Marchamont Nedham (bap. 1620, d. 1678), journalist and pamphleteer. From un- + reasonal.