adjective
1.
Synonyms: illogical , fallacious, invalid, irrational, mad, nonrational, reasonless, sophistic, unreasoned
Related Word: incongruous, loose, self-contradictory
Antonyms: reasonable
2.
exceeding the bounds of reason or right
the constitutional guarantees against unreasonable searches and seizures
Synonyms: unconscionable, undue, unjustifiable, unwarrantable, unwarranted
Related Word: arbitrary, peremptory; excessive, immoderate, inordinate, overmuch; improper, unlawful, unrightful, wrongful
Contrasted words: lawful, licit; proper, right, tolerable
Antonyms: reasonable