chit chat vs chat

chit chat and chat both are nouns.

Word	Noun	Adjective	Verb	Adverb
chit chat	Yes	No	No	No
chat	Yes	No	Yes	No

As nouns, chat is a hypernym of chit chat; that is, chat is a word with a broader meaning than chit chat:

Other hypernyms of chit chat include confab, confabulation, schmoose, schmooze.

chit chat (noun)	chat (noun)
light informal conversation for social occasions	songbirds having a chattering call
	birds having a chattering call
	an informal conversation

chit chat (verb)	chat (verb)
	talk socially without exchanging too much information