Having a round back or shoulders; round-shouldered.(adjective)
Gnu Collaboartive International Dictionary of English: licensed under The Code Project Open License (CPOL)
Use "round-backed" in a sentence
"His innovations in propeller designs helped him to create round-backed Ovation guitars, among the most popular instruments made in the U.S."
"Andela's eighth-floor apartment was cosy, spick and furnished in a style from around 1974 (western calendar) – bamboo-effect bookshelves rising to the ceiling, round-backed wickery chairs, myriad spider plants."
"He was best known for his facility on the lute, a round-backed instrument with a history reaching back to Greek mythology."