witness

Concise Oxford English Dictionary © 2008 Oxford University Press:
witness/ˈwɪtnəs/

▶noun

• 1 a person who sees an event take place.

• 2 a person giving sworn testimony to a court of law or the police.

• 3 a person who is present at the signing of a document and signs it themselves to confirm this.

• 4 evidence; proof.

  ■ open profession of one's religious faith through words or actions.

▶verb

• 1 be a witness to.

• 2 be the place, period, etc. in which (an event or development) takes place.

• 3 be a sign or proof of.

  ■ (witness to) openly profess one's religious faith in.

– origin OE witnes (see wit1, -ness).