crystal clear is an adjective meaning "transmitting light; able to be seen through with clarity". It carries 2 recorded senses.
transmitting light; able to be seen through with clarity
“the cold crystalline water of melted snow”
“crystal clear skies”
“could see the sand on the bottom of the limpid pool”
“lucid air”
“a pellucid brook”
“transparent crystal”
Definitions, synonyms and semantic relations for crystal clear come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.