It is not Spanish but Latin, where horribilis means "horrendous, terrible". See annus horribilis, annus mirabilis.
It is a Latin word meaning horrible, horrific, very ugly, terrifying, terrible. It also means in Latin without fortune, of great misfortune, unfortunate.
HORRIBILIS Latin for horrible . The Latin expression annus HORRIBILIS is used to refer to a year that has not been good.