- swear [ swer ] (past tense swore [ swɔr ] ; past participle sworn [ swɔrn ] ) verb **1. ) intransitive to use words that are deliberately offensive, for example because you are angry with someone:That's the first time I've ever heard him swear.swear at: She was shouting and swearing at everyone.swear profusely: I hammered my thumb and then swore profusely.a ) swear like a trooper INFORMAL to swear a lot2. ) transitive to make a sincere statement that you are telling the truth:swear (that): I swear that's how it happened.She swears that this is the man who attacked her.a ) transitive to make a promise to do something:swear (that): You swore that you would never see her again.swear to do something: He swore to stay out of politics when he retired.swear vengeance against/on someone (=promise to punish them): Marshall swore vengeance against his brother's killers.b ) intransitive or transitive to make a formal promise to be loyal or to tell the truth:Members have to swear an oath of secrecy.swear (your) allegiance to someone (=promise to be loyal): They have to swear allegiance to the Queen.c ) swear to God or swear on my life/the Bible etc. SPOKEN used for emphasizing strongly that you are telling the truth:I swear to God I was never at that place.could have sworn SPOKENused for saying that you are sure that something happened:I could have sworn I already paid that bill.swear someone to secrecy/silenceto make someone promise not to tell anyone else what you have told themswear up and down AMERICANused for emphasizing that something is true:He swore up and down that he had never tried drugs.`swear ,by phrasal verb transitive INFORMALswear by something to believe that something is effective:My father swears by whiskey as a cure for a cold.,swear `in phrasal verb transitiveto make someone give a formal promise in a law court or at an official ceremony:He was sworn in as president.,swear `off phrasal verb transitiveswear off something to promise to stop doing or using something:The headache I got was almost enough to make me swear off wine forever.`swear to phrasal verb transitive usually in negativesswear to something to be completely certain of something:I can't swear to it, but I think I saw Joan yesterday.
Usage of the words and phrases in modern English. 2013.