kitty-cat vs pussycat

kitty-cat and pussycat both are nouns.

Word	Noun	Adjective	Verb	Adverb
kitty-cat	Yes	No	No	No
pussycat	Yes	No	No	No

As nouns, kitty-cat and pussycat are synonyms defined as:

Other synonyms of kitty-cat include kitty, puss, pussy.

kitty-cat (noun)	pussycat (noun)
informal terms referring to a domestic cat	informal terms referring to a domestic cat
	a person who is regarded as easygoing and agreeable