What is the medical term meaning condition of without an opening?

Atresic or imperforate both mean without an opening.

atresia which literally means "without a hold condition". The medical Word part -atreto- is used in medical terms like atretoblepharia, atretocystia, atretogastria, etc.

A mnemonic story to remember this Word part: Your father has brought you a treat (atreto-), "Lifesavers(TM) or doughnuts without a hole".