swear

/sweər/ verb (past tense swore, past participle sworn)

Definition

BAD LANGUAGE [I] › to use language which people think is rude or offensive: He was sent home because he swore at the teacher. She swore loudly and threw the box on the floor.

PROMISE [I, T] › to make a serious promise: [+ to do sth] I swear to tell the truth. [+ (that)] She swore that she was at home at the time of the accident.

TRUE [T] › used to say that you are sure something is true: [+ (that)] I could have sworn that she said she lived in Canterbury (= I was sure she lived in Canterbury, but now I have found that it is not true).

(Definition of swear verb from the Cambridge Learner's Dictionary © Cambridge University Press)