hobbyhorse vs hobby

hobbyhorse and hobby both are nouns.

Word	Noun	Adjective	Verb	Adverb
hobbyhorse	Yes	No	No	No
hobby	Yes	No	No	No

As nouns, hobbyhorse and hobby are synonyms defined as:

hobbyhorse and hobby: a child's plaything consisting of an imitation horse mounted on rockers; the child straddles it and pretends to ride

Other synonyms of hobbyhorse include rocking horse.

hobbyhorse (noun)	hobby (noun)
a child's plaything consisting of an imitation horse mounted on rockers; the child straddles it and pretends to ride	an auxiliary activity
a topic to which one constantly reverts	small Old World falcon formerly trained and flown at small birds
	a child's plaything consisting of an imitation horse mounted on rockers; the child straddles it and pretends to ride