hurdy gurdy vs hurdy-gurdy

hurdy gurdy and hurdy-gurdy both are nouns.

Word	Noun	Adjective	Verb	Adverb
hurdy gurdy	Yes	No	No	No
hurdy-gurdy	Yes	No	No	No

As nouns, hurdy gurdy and hurdy-gurdy are synonyms defined as:

hurdy gurdy and hurdy-gurdy: a stringed instrument that produces sounds by means of a wheel that rubs against the strings

Other synonyms of hurdy gurdy include wheel fiddle.

hurdy gurdy (noun)	hurdy-gurdy (noun)
a stringed instrument that produces sounds by means of a wheel that rubs against the strings	a stringed instrument that produces sounds by means of a wheel that rubs against the strings