Meaning of “betray” in the English Dictionary

"betray" in British English

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betrayverb [ T ]

us uk /bɪˈtreɪ/

betray verb [ T ] (NOT LOYAL)

B2 to not be loyal to your country or a person, often by doing something harmful such as helping their enemies:

He was accused of betraying his country during the war.
She felt betrayed by her mother's lack of support.
For years they betrayed the UK's secrets to Russia.
formal He promised never to betray his wife (= never to leave her for another person).

formal If someone betrays something such as a promise, they do not do what they promised:

The president has been accused of betraying his election promises.
By staying out so late, they have betrayed my trust (= disappointed me because I had trusted them not to).

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(Definition of “betray” from the Cambridge Advanced Learner’s Dictionary & Thesaurus © Cambridge University Press)

"betray" in American English

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betrayverb [ T ]

us /bɪˈtreɪ/

betray verb [ T ] (BE NOT LOYAL)

to be not loyal to your country or to someone who believes you are loyal, often by doing something harmful:

Some lawmakers say they feel betrayed by the president.

betray verb [ T ] (SHOW)

to show your feelings or thoughts without intending to:

She could not help betraying her sympathy for us.

(Definition of “betray” from the Cambridge Academic Content Dictionary © Cambridge University Press)