As someone who both studied philosphy and product design I'd argue: A table is, what can be used as a table.

Heidegger would probably say something like "the table tables" (more on brand in German "Der Tisch tischt") - so a table is a thing that supports tablelike actions.

Of course "table-like" is a gradient instead of a binary flag. An archetypical four-legged table is the way you might draw a table when asked about it — so it might — for that individual living at that time in bistory be as table-like as it gets. However, there are totally recognizable tables with just one leg, or even with no legs (e.g. carved into a stone wall) or with alternative ways of suspensions (hanging from the ceiling, mounted on the wall, etc). In the end even a rock could act as your table when you are out hiking. Of course you still recognize it as a rock, but it has shown table-like qualities now, it can be your table for the moment.

Then there are also different kind of tables: work benches, kitchen tables, desks, coffe tables, long and thin tables, more akin to shelves, but used as tables, folding tables, tables with rolls on them etc. They can totally differ in their proportions and usage, yet we call them tables, mostly because ofhers will know which object we mean, when we say it. When you however demanded a table at work and they gave you a tiny coffee table you would exclaim: "This is not a table!". Rightfully so, for the context you are in it is not useful (it differs too much from an office table).

So if instead of asking if something is a table, asking whether something can be used as a table (if it has table-like qualities to it) is more like how I think object-subject relations work in practise. We call things a table because we use it as a table. We don't call things a table because somewhere out there in the universe exists a clear definition of what the concept of said table constitutes.

If you were to shoot a film or direct a theatre play, then you wouldn't be interested in whether in principle the object can be used as a table, you would be interested in it's readability as a table that hints to the viewer a certain millieu or social background. This might also be something you'd consider when the primary purpose of your table/desk is to impress your subordinates.

Of course the table-like quality of an object would be just one of its many dimensions. One could also go in and ask about arbitrary dimensions like the bulkyness of the object, about the intentionality (that hiking picnick rock is a table, but an unintentional one). One could ask about many aspects that constitute subject-object relations, however it is important not to forget that in our daily lives we just ballpark these categories intuitively. So what I might still call a table might not at all be seen as a table by another person ("This is not a table, it is a rock") and yet both of us a right and wrong at the same time.

Interestingly AI goes a lot into looks, where the dimension of usability might be more useful (but harder to extract from images). So internally an AI would represent table-likeness as a floating point number and only says something is (or isn't) a table based on thresholds somebody found useful.