■ noun a substance which does not readily allow the passage of heat, sound, or electricity.
↘a block of glass, ceramic, or other insulating material enclosing an electric wire where it crosses a support.
■ noun a substance which does not readily allow the passage of heat, sound, or electricity.
↘a block of glass, ceramic, or other insulating material enclosing an electric wire where it crosses a support.
Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004