Is there a name for a window without glass?
I am speaking of a barn or log cabin which has a window opening but no glass. Neither "window" nor "opening" seem quite right.
A fire blocked the cabin's only door. Fortunately, I squeezed through the _______ and escaped to safety.
Actually, a window ("wind-eye") was originally an unglazed opening to let in light and air ("wind"). In modern English it is still possible to use "window" for an opening without glass.
It's just called a window. If for some reason you really need to call attention to the fact that it doesn't have glass in it, you could call it an unglazed window.
Unglazed
- having no glass fitted
an unglazed circular skylight
https://www.collinsdictionary.com/us/dictionary/english/unglazed
As others have said you could just use the word window. If you want to emphasise that there is not glass pane in it, I would use frame or window frame.
the frame of a window that receives and holds the sashes or casements
According to Merriam Webster
Neither "window" nor "opening" seem quite right.
However, both "window" and "opening" when used together do.
A fire blocked the cabin's only door. Fortunately, I squeezed through the window opening and escaped to safety.
Construction sites and references I located use the window-modified term "opening" for the location where a gap for a window opening will be framed, cut, and installed.
Thereafter, the finished assembly continues to be referenced as a "window" which can be opened, closed, cleaned, broken, repaired, etc.
Given that the construction industry has a bias against incomplete structures, the term window refers more to the intended function of the feature rather than the actual construction and architectural treatment of it.