unilateral

American  

[yoo-nuh-lat-er-uhl] / ˌyu nəˈlæt ər əl /

adjective

1. relating to, occurring on, or involving one side only.

   unilateral development; a unilateral approach.

2. undertaken or done by or on behalf of one side, party, or faction only; not mutual.

   a unilateral decision; unilateral disarmament.

3. having only one side or surface; without a reverse side or inside, as a Möbius strip.

4. Law.

   1. pertaining to a contract that can be formed only when the party to whom an offer is made renders the performance for which the offeror bargains.

   2. pertaining to a contract in which obligation rests on only one party, as a binding promise to make a gift.

5. Botany. having all the parts disposed on one side of an axis, as an inflorescence.

6. through forebears of one sex only, as through either the mother's or father's line.

7. Phonetics. (of an l -sound) characterized by passage of air on only one side of the tongue.

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unilateral British  

/ ˌjuːnɪˈlætərəl /

adjective

1. of, having, affecting, or occurring on only one side

2. involving or performed by only one party of several

   unilateral disarmament

3. law (of contracts, obligations, etc) made by, affecting, or binding one party only and not involving the other party in reciprocal obligations

4. botany having or designating parts situated or turned to one side of an axis

5. sociol relating to or tracing the line of descent through ancestors of one sex only Compare bilateral

6. phonetics denoting an (l) sound produced on one side of the tongue only

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Other Word Forms

• unilateralism noun
• unilaterality noun
• unilaterally adverb

Etymology

Origin of unilateral

From the New Latin word ūnilaterālis, dating back to 1795–1805. See uni-, lateral

Explanation

Unilateral means "one-sided." If parents make a unilateral decision to eliminate summer vacation, it means that the students’ opinions or opposing views weren’t considered. When someone makes a unilateral decision, he or she acts alone, without considering the feelings, opposing opinions or concerns of others. But it’s not always a bad thing to act unilaterally. If you are in a fight with your sister and haven’t spoken to each other for a week, you could choose to do her chores, compliment her or make other unilateral, good-faith efforts to bring the bad feelings to an end.

Example Sentences

They can make major unilateral decisions — such as welcoming federal troops into California cities — and command a bully pulpit to drive public opinion and policy, including through statewide ballot measures.

From Los Angeles Times • Apr. 9, 2026

On a special Slate Plus extra episode of Amicus, Mark Joseph Stern spoke with Eugene Fidell about Trump’s startling claim of unilateral war powers.

From Slate • Mar. 2, 2026

In 1973 it adopted the War Powers Resolution, passed over Richard Nixon's veto, to become the only lasting limit on unilateral presidential military action abroad.

From Barron's • Feb. 28, 2026

A family spokesperson said: “Alice de Rothschild’s university admissions in the United States, as well as her rejections, are entirely due to her grades. Alice cannot be held responsible for Jeffrey Epstein’s unilateral actions.”

From The Wall Street Journal • Feb. 26, 2026

And I can see by the look in her eye that she’s freefalling toward a unilateral decision.

From "Dry" by Neal Shusterman and Jarrod Shusterman