Definition of Silica 1. A white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechatelierite Noun Synonyms for word "silica" Semanticaly linked words with "silica" Hyponims for word "silica" Lexical Analysis for "silica" siliceous relating to or containing or resembling silica silicious relating to or containing or resembling silica etymology felsic etymology silcrete etymology silicon etymologically related silicate etymologically related silicon etymological origin of silex [Irish] is derived from silica gel is derived from silica glass is derived from silica wool is derived from silicas is derived from silicate is derived from siliceous is derived from silici- is derived from silicic is derived from silicide