ponycart vs pony cart

ponycart and pony cart both are nouns.

Word	Noun	Adjective	Verb	Adverb
ponycart	Yes	No	No	No
pony cart	Yes	No	No	No

As nouns, ponycart and pony cart are synonyms defined as:

Other synonyms of ponycart include donkey cart, tub-cart.

ponycart (noun)	pony cart (noun)
a cart with an underslung axle and two seats	a cart with an underslung axle and two seats