Real Dictionary

tortoiseshell
Tortoiseshell means made of tortoiseshell or made of a material which resembles tortoiseshell.
uncountable noun: Tortoiseshell is the hard shell of a kind of sea turtle. It is brown and yellow in colour and is often polished and used to make jewellery and ornaments.

tortoiseshell in American English
the hard, mottled, yellow-and-brown shell of some turtles and tortoises, used in inlaying and, esp. formerly, in making combs, frames for eyeglasses, etc.
adjective: mottled or variegated like tortoiseshell, esp. with yellow and brown and sometimes other colors
noun: a horny substance of a mottled brown and yellow coloration, composing the laminae that cover the inner body plates of the carapace of a hawksbill turtle, used for making combs and ornamental articles, inlaying, etc

tortoiseshell in British English
noun: a horny translucent yellow-and-brown mottled substance obtained from the outer layer of the shell of the hawksbill turtle: used for making ornaments, jewellery, etc