Definition of testify

• v. i. - To make a solemn declaration, verbal or written, to establish some fact; to give testimony for the purpose of communicating to others a knowledge of something not known to them.
• v. i. - To make a solemn declaration under oath or affirmation, for the purpose of establishing, or making proof of, some fact to a court; to give testimony in a cause depending before a tribunal.
• v. i. - To declare a charge; to protest; to give information; to bear witness; -- with against.
• v. t. - To bear witness to; to support the truth of by testimony; to affirm or declare solemny.
• v. t. - To affirm or declare under oath or affirmation before a tribunal, in order to prove some fact.
• adv. - In a testy manner; fretfully; peevishly; with petulance.