WordNet Dictionary- [v] exhibit a play of colors like that of an opal; "This nitrate opalesces under certain conditions"
- [v] reflect light or colors like an opal; "Distant clouds opalesce like pale brocade"; "raindrops caught in a sunbeam seem to opalesce"
Webster's 1913 Dictionary\O`pal*esce"\, v. i. [imp. & p. p. {Opalesced}; p. pr.
& vb. n. {Opalescing}.]
To give forth a play of colors, like the opal.