visualiser vs beholder

visualiser and beholder both are nouns.

Word	Noun	Adjective	Verb	Adverb
visualiser	Yes	No	No	No
beholder	Yes	No	No	No

As nouns, beholder is a hypernym of visualiser; that is, beholder is a word with a broader meaning than visualiser:

visualiser: one whose prevailing mental imagery is visual
beholder: a person who becomes aware (of things or events) through the senses

Other hypernyms of visualiser include observer, perceiver, percipient.

visualiser (noun)	beholder (noun)
one whose prevailing mental imagery is visual	a person who becomes aware (of things or events) through the senses