adj. Exhibiting a milky iridescence like that of an opal.
the GNU version of the Collaborative International Dictionary of English
adj. Reflecting a milky or pearly light from the interior; having an opaline play of colors.
The Century Dictionary and Cyclopedia
Having variegated and changing colors like those of the opal.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. having a play of lustrous rainbow colors
"To the observer of the aura the term "opalescent" instinctly presents itself, for there is a striking resemblance to the opaline peculiar play of colors of delicate tints and shades in a body of pearly or milky hue."