witnesser vs speaker

witnesser and speaker both are nouns.

Word	Noun	Adjective	Verb	Adverb
witnesser	Yes	No	No	No
speaker	Yes	No	No	No

As nouns, speaker is a hypernym of witnesser; that is, speaker is a word with a broader meaning than witnesser:

witnesser: someone who sees an event and reports what happened
speaker: someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)

Other hypernyms of witnesser include beholder, observer, perceiver, percipient, talker, utterer, verbaliser, verbalizer.

witnesser (noun)	speaker (noun)
someone who sees an event and reports what happened	electro-acoustic transducer that converts electrical signals into sounds loud enough to be heard at a distance
	someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)