bran·chi·os·te·gal I. \|braŋkē|ästə̇gəl\adjective Etymology: International Scientific Vocabulary branchi- + steg- + -al : of or relating to the branchiostegals < the branchiostegal membrane > II. noun orbranchiostegal ray (-s) : one of the bony radiating processes of the hyoid arch that support the membranes enclosing the gill chamber in most fishes