red dwarf

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A dwarf star, ranging in mass from one-tenth to one-half the mass of the sun, whose relatively cool surface temperature makes it appear red-orange in color.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun astronomy A small, relatively cool star of the main sequence; most stars in the Milky Way are red dwarfs.

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

• noun a small, old, relatively cool star; approximately 100 times the mass of Jupiter