二叠系 èrdiéxì Permian System Origin Definitions Defs Strokes Stroke Words Sentences Sents 二 èr numeral two the number two; 2叠 疊 dié verb to pile up To pile up or stack; to accumulate layer by layer系 xì system (geology) (geology) a chronostratigraphic unit of rocks formed during a period of geological time, ranking below an erathem and above a series