Definition of "opal" in English

noun

1. (mineralogy) A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula SiO₂·nH₂O.

2. The colour of opal: any shade of blue with bright flecks of other colours, such as white, yellow, and red.

3. (biology, genetics, biochemistry) A colloquial name used in molecular biology referring to a particular stop codon sequence, "UGA."

4. Any of various lycaenid butterflies of the genus Nesolycaena.