Antonyms of adj unreasonable

2 senses of unreasonable

Sense 1
unreasonable (vs. reasonable) -- (not reasonable; not showing good judgment)

reasonable (vs. unreasonable), sensible -- (showing reason or sound judgment; "a sensible choice"; "a sensible person")
        => commonsense, commonsensible, commonsensical -- (exhibiting native good judgment; "arrive home at a reasonable hour"; "commonsense scholarship on the foibles of a genius"; "unlearned and commonsensical countryfolk were capable of solving problems that beset the more sophisticated")
        => healthy, intelligent, levelheaded, level-headed, sound -- (exercising or showing good judgment; "healthy scepticism"; "a healthy fear of rattlesnakes"; "the healthy attitude of French laws"; "healthy relations between labor and management"; "an intelligent solution"; "a sound approach to the problem"; "sound advice"; "no sound explanation for his decision")
        => tenable, well-founded -- (based on sound reasoning or evidence; "well-founded suspicions")

Sense 2
excessive, inordinate, undue, unreasonable -- (beyond normal limits; "excessive charges"; "a book of inordinate length"; "his dress stops just short of undue elegance"; "unreasonable demands")

INDIRECT (VIA immoderate) -> moderate -- (being within reasonable or average limits; not excessive or extreme; "moderate prices"; "a moderate income"; "a moderate fine"; "moderate demands"; "a moderate estimate"; "a moderate eater"; "moderate success"; "a kitchen of moderate size"; "the X-ray showed moderate enlargement of the heart")

Similarity of adj unreasonable

2 senses of unreasonable

Sense 1
unreasonable (vs. reasonable) -- (not reasonable; not showing good judgment)
       => counterintuitive -- (contrary to what common sense would suggest)
       => indefensible, untenable -- ((of theories etc) incapable of being defended or justified)
       => mindless, reasonless, senseless -- (not marked by the use of reason; "mindless violence"; "reasonless hostility"; "a senseless act")
       => undue, unjustified, unwarranted -- (lacking justification or authorization; "desire for undue private profit"; "unwarranted limitations of personal freedom")
          Also See-> illogical#1, unlogical#1; immoderate#1; irrational#1

Sense 2
excessive, inordinate, undue, unreasonable -- (beyond normal limits; "excessive charges"; "a book of inordinate length"; "his dress stops just short of undue elegance"; "unreasonable demands")
       => immoderate (vs. moderate) -- (beyond reasonable limits; "immoderate laughter"; "immoderate spending")