The phrase "perjured oneself" refers to giving false testimony while under oath. Synonyms for this term include committing perjury, bearing false witness, giving false testimony, and lying under oath. Other related phrases that might be used in place of "perjured oneself" include false swearing, deceiving the court, or committing an act of perjury. These terms are often used in legal contexts, such as during a trial or hearing, and can carry serious consequences for those who are found to have perjured themselves. While it is always important to tell the truth, it is especially important when giving testimony under oath.