having a play of lustrous rainbow-like colors; "an iridescent oil slick"; "nacreous (or pearlescent) clouds looking like mother-of-pearl"; "a milky opalescent (or opaline) luster"

wine with milky glints reminiscent of opal

Reflecting an iridescent light; having a milky iridescence.

a translucent glass which transmits less light that a transparent glass, but more than a waxy or opaque glass. Varies in degree from "clam broth" to near waxy.

Reflecting an iridescent light; having a colored smooth surface that gives the effect of cloudiness and diffusion due to the intentional presence of fissures, striae, and bubbles.

This refers to how much light a type of glass transmits. Opalescent glass does not allow much light to pass straight through, and these types of glass are often used for lamp shades, because the opacity of the glass will hide the filament of a light bulb and diffuse the light in a soft way. Opalescent glass cannot be seen through- anything appearing behind it will not be visible in front of the glass, other than perhaps a shadow.

A material with a cloudy-white translucent appearance - like an Opal.

Typically iridescent - usually milky or translucent.