tortoiseshell vs tortoiseshell-cat

tortoiseshell and tortoiseshell-cat both are nouns.

Word	Noun	Adjective	Verb	Adverb
tortoiseshell	Yes	No	No	No
tortoiseshell-cat	Yes	No	No	No

As nouns, tortoiseshell and tortoiseshell-cat are synonyms defined as:

tortoiseshell and tortoiseshell-cat: a cat having black and cream-colored and yellowish markings

Other synonyms of tortoiseshell include calico cat.

tortoiseshell (noun)	tortoiseshell-cat (noun)
a cat having black and cream-colored and yellowish markings	a cat having black and cream-colored and yellowish markings
brilliantly colored; larvae feed on nettles
the mottled horny substance of the shell of some turtles