Nonmetal describes an element that doesn’t have the characteristics of metal including: ability to conduct heat or electricity, luster, or flexibility. (adjective)
See nonmetal in Webster's New World College Dictionary
noun
any of those elements lacking the characteristics of a metal; specif., any of the electronegative elements (e.g., oxygen, carbon, nitrogen, fluorine, phosphorus, sulfur) whose oxides form acids and stable compounds with hydrogen