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

In the business realm, the ‘expert’ will be the one who provides insights, expertise, and unique value that is economically unreasonable to source any other way. —Big Think, 26 Nov. 2025

This egregious behavior was unreasonable and over-the-top. —Todd Feurer, CBS News, 25 Nov. 2025

With so few opportunities to gather as a family, the Reddit user couldn’t help wondering whether asking to bring the dogs anyway was an unreasonable request. —Tereza Shkurtaj, PEOPLE, 23 Nov. 2025

Immigration enforcement operations without a warrant or without announcing themselves can raise questions about Fourth Amendment protections against unreasonable searches and seizures. —Billal Rahman, MSNBC Newsweek, 21 Nov. 2025

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