unreasonable

adjective

un·​rea·​son·​able

ˌən-ˈrēz-nə-bəl, 

-ˈrē-zᵊn-ə-bəl 

1

a

: not governed by or acting according to reason

unreasonable people

b

: not conformable to reason : absurd

unreasonable beliefs

2

a

: exceeding the bounds of reason, appropriateness, or moderation

working under unreasonable pressure

an unreasonable restraint of trade

b

: lacking justification

an unreasonable inference

unreasonableness

ˌən-ˈrēz-nə-bəl-nəs, 

-ˈrē-zᵊn-ə-bəl- 

noun

unreasonably

ˌən-ˈrēz-nə-blē, 

-ˈrē-zᵊn-ə-blē 

adverb

Synonyms of unreasonable

• irrational
• unwarranted
• unfounded
• baseless
• unsupported
• invalid
• unnecessary
• groundless
• unsubstantiated
• unreasoned
• absurd
• false
• illogical

Examples of unreasonable in a Sentence

I told him that I wouldn't pay unless he sent me a replacement. Am I being unreasonable?

You are entitled to compensation for unreasonable delays.

Recent Examples on the Web

This violates the 4th Amendment, which protects people (including noncitizens) from unreasonable searches and seizures in their homes. —Arkansas Online, 16 Feb. 2026

There are people who desire to drastically improve the health of our ecosystems who unknowingly struggle with unreasonable expectations. —Chris McKeown, Cincinnati Enquirer, 14 Feb. 2026

Amid those pressures, many people turn to the comfort of a pet – but the expectations for what dogs can bring to our lives are becoming increasingly unreasonable. —Margret Grebowicz, Fortune, 13 Feb. 2026

Several speakers said the restrictions put forward in the measure would put an unreasonable burden on service providers and facilities, who would be held liable if people seeking support are using or possessing drugs without their knowledge. —Robin Opsahl, Iowa Capital Dispatch, 13 Feb. 2026

Word History

First Known Use

14th century, in the meaning defined at sense 1a

Legal Definition

unreasonable

adjective

un·​rea·​son·​able

: not reasonable : beyond what can be accepted: as

a

: clearly inappropriate, excessive, or harmful in degree or kind

an unreasonable delay

an unreasonable restraint of trade

b

: lacking justification in fact or circumstance

an unreasonable inference

especially : irrational sense b

the agency decision was unreasonable

c

: not supported by a warrant or by a valid exception to a warrant requirement (as when there is reasonable suspicion) and therefore unconstitutional

the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated

—U.S. Constitution amend. IV

see also search, seizure

unreasonableness noun

unreasonably adverb