gymnast vs tumbler

gymnast and tumbler both are nouns.

Word	Noun	Adjective	Verb	Adverb
gymnast	Yes	No	No	No
tumbler	Yes	No	No	No

As nouns, tumbler is a hyponym of gymnast; that is, tumbler is a word with a more specific, narrower meaning than gymnast:

gymnast (noun)	tumbler (noun)
an athlete who is skilled in gymnastics	pigeon that executes backward somersaults in flight or on the ground
	a glass with a flat bottom but no handle or stem; originally had a round bottom
	a movable obstruction in a lock that must be adjusted to a given position (as by a key) before the bolt can be thrown
	a gymnast who performs rolls and somersaults and twists etc.