pony cart vs tub-cart

pony cart and tub-cart both are nouns.

Word	Noun	Adjective	Verb	Adverb
pony cart	Yes	No	No	No
tub-cart	Yes	No	No	No

As nouns, pony cart and tub-cart are synonyms defined as:

Other synonyms of pony cart include donkey cart, ponycart.

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