soap bubble

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

• noun A bubble, especially a large one, formed from soapy water.
• noun Something beautiful but transient or illusory.

from The Century Dictionary.

• noun A bubble formed from soapy water; especially, a thin spherical film of soap-suds inflated by blowing through a pipe, and forming a hollow globe which has often beautiful iridescent colors playing over the surface.

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

• noun A very thin film of soap water that forms a sphere with an iridescent surface.

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

• noun a bubble formed by a thin soap film