The word opaque can be used in several different contexts, most commonly as an adjective, though there are historical and obscure instances of the word being used as a noun. It can also be used as a transitive verb, as in to make something opaque.
Opaque is thought to stem from the Latin word opacus, meaning shaded, shady and dark. The current spelling probably dates from the 1800s and was taken from the French word opaque.
Opaque simply means "not transparent," and "blocking light." It can also be used to mean "impenetrable" as well as to describe someone who is stupid.
Use as a Noun
As a noun, opaque refers to an area of complete darkness. This use of the word is most commonly found in poetry. Opaque can also refer to an object, such as clothing or paint, that is not transparent.
Use as a Verb
Opaque also functions as a transitive verb. To opaque something is to make it dark, obscure, or not to see through.
Use In Linguistics
In linguistics, opaque refers to a word whose meaning is not readily apparent and cannot be inferred from its sound or shape.