chili vs chili pepper

chili and chili pepper both are nouns.

Word	Noun	Adjective	Verb	Adverb
chili	Yes	No	No	No
chili pepper	Yes	No	No	No

As nouns, chili and chili pepper are synonyms defined as:

chili and chili pepper: very hot and finely tapering pepper of special pungency

Other synonyms of chili include chile, chilli, chilly.

chili (noun)	chili pepper (noun)
very hot and finely tapering pepper of special pungency	very hot and finely tapering pepper of special pungency
ground beef and chili peppers or chili powder often with tomatoes and kidney beans	plant bearing very hot and finely tapering long peppers; usually red