an extra door that is put on the usual door for protection in bad weather

I went up her front steps, opened the storm door and knocked. 我走上她家门前的台阶，打开外重门，敲了敲房门。

A storm door with a broken latch banged against the back porch. 坏了插销的外重门碰在后门廊的墙上呯呯作响。