Need help understanding the definition of 吹き抜け


I was reading the definition of the word 吹き抜け from Daijirin:

> ふき ぬけ [0] 【吹（き）抜け】
>
>
> ②〘建〙家屋で，柱の間に壁がなく外部に開放されていること。また，建物の内部で二階または数階貫通して床を設けず，上下がつながった構造になっていること。ふきはなし。ふきぬき。

I have trouble making sense of this sentence even after looking at some images
of 吹き抜け

> 家屋で，柱の間に壁がなく外部に開放されていること。

It seems to mean there are no walls between rooms and is exposed to outside? I
am not sure about the meanings of 壁 and 外部に開放されている.




I suppose [this
definition](https://kotobank.jp/word/%E5%90%B9%E6%8A%9C-2079362) is clearer:

> さえぎるものがなく、風が自由に吹き通ること。また、その所。吹きはらい。

What is commonly referred to as 吹き抜け is '二階または数階貫通して床を設けず，上下がつながった構造になっていること'.
This means that a part of the ceiling is removed and there is no 'wall'
vertically. Outside houses, the most typical is the structure of shopping
malls where there is no ceilings at the center (in Japan, typically, an AEON).

As for '家屋で，柱の間に壁がなく外部に開放されていること。', this should mean horizontal wallless-ness.
I think the definition is vague, and as far as I can think of, 外部に開放されている does
not mean more than a room without a wall ( _exposed to the outside of the
room_ ).




I suppose [this
definition](https://kotobank.jp/word/%E5%90%B9%E6%8A%9C-2079362) is clearer:

> さえぎるものがなく、風が自由に吹き通ること。また、その所。吹きはらい。

What is commonly referred to as 吹き抜け is '二階または数階貫通して床を設けず，上下がつながった構造になっていること'.
This means that a part of the ceiling is removed and there is no 'wall'
vertically. Outside houses, the most typical is the structure of shopping
malls where there is no ceilings at the center (in Japan, typically, an AEON).

As for '家屋で，柱の間に壁がなく外部に開放されていること。', this should mean horizontal wallless-ness.
I think the definition is vague, and as far as I can think of, 外部に開放されている does
not mean more than a room without a wall ( _exposed to the outside of the
room_ ).

