By that, then, you mean undefined.

It once meant that three features appeared: encapsulation, inheritance, and constrained runtime binding.

Any time it is used without implying those, it is just more or less noise.

That said, OO has become a niche technique: it fits certain problem spaces well, others very badly. Any big enough system will have some parts that could meaningfully be described as mostly OO. But there is no value in purity, so none in distinguishing those bits, particularly, or excluding non-OO notions there.

Trying to cram all solutions into the OO shoe by providing no support for any other organization (cough Java) damaged the brand, probably irreparably. It still makes sense to say part of a system has an OO flavor, for exposition, but there is little value, otherwise.