champion vs champ

champion and champ both are nouns.

Word	Noun	Adjective	Verb	Adverb
champion	Yes	Yes	Yes	No
champ	Yes	No	Yes	No

As nouns, champion and champ are synonyms defined as:

Other synonyms of champion include title-holder.

champion (noun)	champ (noun)
someone who fights for a cause	someone who has won first place in a competition
someone who has won first place in a competition
a person who backs a politician or a team etc.
someone who is dazzlingly skilled in any field

champion (adjective)	champ (adjective)
holding first place in a contest

champion (verb)	champ (verb)
protect or fight for as a champion	chew noisily or vigorously
	chafe at the bit, like horses