swear / swe(ə)r/ • v. (past swore / swôr/ ; past part. sworn / swôrn/ ) 1. make a solemn statement or promise undertaking to do something or affirming that something is the case: Maria made me swear I would never tell anyone I swear by all I hold dear that I had nothing to do with it | he swore to obey the rules | [with direct speech] “Never again,” she swore, “will I be short of money” | [tr.] they were reluctant to swear allegiance. ∎ [tr.] take (an oath): he forced them to swear an oath of loyalty to him. ∎ [tr.] take a solemn oath as to the truth of (a statement): I asked him if he would swear a statement to this effect. ∎ [tr.] (swear someone in) admit someone to a particular office or position by directing them to take a formal oath: he was sworn in as president on July 10. ∎ [tr.] make (someone) promise to observe a certain course of action: I've been sworn to secrecy. ∎ [intr.] (swear to) express one's assurance that something is the case: I couldn't swear to it, but I'm pretty sure it's his writing. ∎ [intr.] (swear off) inf. promise to abstain from: I'd sworn off alcohol. ∎ [intr.] (swear by) inf. have or express great confidence in the use, value, or effectiveness of: Iris swears by her yoga.2. [intr.] use offensive language, esp. as an expression of anger: Peter swore under his breath.PHRASES: swear up and down inf. affirm something emphatically: he swore up and down they'd never get him up on that stage.PHRASAL VERBS: swear something out Law obtain the issue of (a warrant for arrest) by making a charge on oath.DERIVATIVES: swear·er n.