Peeping Tom vs peeper

Peeping Tom and peeper both are nouns.

Word	Noun	Adjective	Verb	Adverb
Peeping Tom	Yes	No	No	No
peeper	Yes	No	No	No

As nouns, Peeping Tom and peeper are synonyms defined as:

Peeping Tom and peeper: a viewer who enjoys seeing the sex acts or sex organs of others

Other synonyms of Peeping Tom include voyeur.

Peeping Tom (noun)	peeper (noun)
a viewer who enjoys seeing the sex acts or sex organs of others	an animal that makes short high-pitched sounds
	an informal term referring to the eye
	a viewer who enjoys seeing the sex acts or sex organs of others