binary star

from The American Heritage® Dictionary of the English Language, 4th Edition

• n. A stellar system consisting of two stars orbiting about a common center of mass and often appearing as a single visual or telescopic object. Also called double star.

from Wiktionary, Creative Commons Attribution/Share-Alike License

• n. A stellar system that has two stars orbiting around each other; double star.

from the GNU version of the Collaborative International Dictionary of English

• adj. a double star whose members have a revolution round their common center of gravity.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• n. a system of two stars that revolve around each other under their mutual gravitation