(noun.) two words that can be interchanged in a context are said to be synonymous relative to that context.
手打:路易
双语例句
It was with such a furnace probably that India produced her keen-edged weapons that would cut a web of gossamer, and Damascus its flashing blades--the synonym of elastic strength. 威廉·亨利·杜利特.世纪发明.
It is not possible to define these ideas except by synonyms, like coming home to one really taking it in, etc. 约翰·杜威.民主与教育.