In law, a witness is someone who, either voluntarily or under compulsion, provides testimonial evidence, either oral or written, of what they know or claim to know. 6 days ago · certify, attest, witness, vouch mean to testify to the truth or genuineness of something. certify usually applies to a written statement, especially one carrying a signature or seal. attest applies … To witness something is to see, hear, sense, or know something, as in I witnessed our dog running out the door, but I didn’t see where she went. witness synonyms, witness pronunciation, witness translation, English dictionary definition of witness. One who can give a firsthand account of something seen, heard, or experienced: a … Definition of Witness in the Definitions.net dictionary. What does Witness mean? Information and translations of Witness in the most comprehensive dictionary definitions resource on … a person who has witnessed something, esp. one who is able to declare what has taken place:[countable] a witness to the accident. [countable] a person who gives testimony, as in a court of law. English dictionary and integrated thesaurus for learners, writers, teachers, and students with advanced, intermediate, and beginner levels.