unilateral

adjective

uni·​lat·​er·​al ˌyü-ni-ˈla-tə-rəl 

-ˈla-trəl

1

a

: done or undertaken by one person or party

b

: of, relating to, or affecting one side of a subject : one-sided

c

: constituting or relating to a contract or engagement by which an express obligation to do or forbear is imposed on only one party

2

a

: having parts arranged on one side

a unilateral raceme

b

: occurring on, performed on, or affecting one side of the body or one of its parts

unilateral exophthalmos

3

: unilineal

4

: having only one side

unilaterally adverb

Did you know?

The world is a smaller place than it used to be, and we get uncomfortable when a single nation adopts a policy of unilateralism—that is, acting independently with little regard for what the rest of the world thinks. A unilateral invasion of another country, for instance, usually looks like a grab for power and resources. But occasionally the world welcomes a unilateral action, as when the U.S. announced unilateral nuclear-arms reductions in the early 1990s. Previously, such reductions had only happened as part of bilateral ("two-sided") agreements with the old Soviet Union. Multilateral agreements, on issues such as climate change, often involve most of the world's nations.

Examples of unilateral in a Sentence

Our country is prepared to take unilateral action.

Recent Examples on the Web

At the same time, Trump's unilateral action also builds on Democrats' message of Trump pushing the bounds of his authority in all aspects of the presidency. —Domenico Montanaro, NPR, 23 June 2025

My statement on Donald Trump’s unilateral military action in Iran. —Anna Commander, MSNBC Newsweek, 22 June 2025

There was no urgency that suggested, while diplomatic talks were underway, that the U.S. should take this unilateral action by President Trump's orders yesterday. —CBS News, 22 June 2025

Key Background Tensions between Iran and Israel first erupted on Friday, when the Israel military carried out unilateral strikes against key nuclear facilities and killed several top Iranian generals and nuclear scientists. —Siladitya Ray, Forbes.com, 21 June 2025

Word History

First Known Use

1802, in the meaning defined at sense 1a

Rhymes for unilateral

• basolateral
• contralateral
• dorsolateral
• equilateral
• ipsilateral
• multilateral
• quadrilateral
• ventrolateral
• anterolateral
• posterolateral
• bilateral
• collateral

Kids Definition

unilateral

adjective

uni·​lat·​er·​al ˌyü-ni-ˈlat-ə-rəl 

-ˈla-trəl

: done or carried out by only one of two or more parties

unilateral disarmament

unilaterally

-ē

adverb

Medical Definition

unilateral

adjective

uni·​lat·​er·​al ˌyü-ni-ˈlat-ə-rəl, -ˈla-trəl 

: occurring on, performed on, or affecting one side of the body or one of its parts

unilateral exophthalmos

unilaterally

-ē 

adverb

Legal Definition

unilateral

adjective

uni·​lat·​er·​al ˌyü-nə-ˈla-tə-rəl 

1

: done or undertaken by one party

a unilateral mistake as to the terms

2

: of, relating to, or affecting one side of a subject

3

: containing a promise to perform made by only one party especially because the other has already performed (as by paying an amount)

an option contract is unilateral

unilaterally adverb