chin vs chin up

chin is a noun but chin up is not a noun.

Word	Noun	Adjective	Verb	Adverb
chin	Yes	No	Yes	No
chin up	No	No	Yes	No

As verbs, chin and chin up are synonyms defined as:

chin and chin up: raise oneself while hanging from one's hands until one's chin is level with the support bar

chin (noun)	chin up (noun)
the protruding part of the lower jaw

chin (verb)	chin up (verb)
raise oneself while hanging from one's hands until one's chin is level with the support bar	raise oneself while hanging from one's hands until one's chin is level with the support bar