gas giant

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

• noun A large planet having a thick gaseous atmosphere but no solid surface due to a low abundance of rock or other solid material. Jupiter, Saturn, Uranus, and Neptune are gas giants.

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

• noun A large planet composed mostly of gaseous hydrogen and helium, along with methane and ammonia; possibly with a solid core.

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

• noun any of the four outermost planets in the solar system; much larger than Earth and gaseous in nature (like Jupiter)