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Synonyms for Witness (same or very similar meaning)

WordNet sense 1 ((law) a person who attests to the genuineness of a document or signature by adding their own signature):
attestant, attestator, attestor

WordNet sense 2 (someone who sees an event and reports what happened):
informant, witnesser

WordNet sense 3 (a close observer; someone who looks at something (such as an exhibition of some kind)):
looker, spectator, viewer, watcher

WordNet sense 4 (perceive or be contemporaneous with):
find, see

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