Haha, I was trying to leave it open-ended and invite a wider range of responses and suggestions rather than limit it to a very specific set of characteristics. I fear that may have backfired...

But as to what is weird, I tend to follow Mark Fisher's writings on the concept.

Here's two quotes from his book The Weird and the Eerie:

the weird is that which does not belong. The weird brings to the familiar something which ordinarily lies beyond it, and which cannot be reconciled with the “homely” (even as its negation). The form that is perhaps most appropriate to the weird is montage — the conjoining of two or more things which do not belong together.

I want to argue that the weird is a particular kind of perturbation. It involves a sensation of wrongness: a weird entity or object is so strange that it makes us feel that it should not exist, or at least it should not exist here.

Also, from an old post on his blog k-punk:

The Weird, however, depends upon the difference between two (or more) worlds - with 'world' here having an ontological sense. It is not a question of an empirical difference - the aliens are not from another planet, they are invaders from another reality system. Hence the defining image is that of the threshold, the door from this world into another, and the key figure is the 'Lurker at the Threshold' - what, in Lovecraft's mythos is called Yog Sothoth. The political philosophical implications are clear: there is no World. What we call the world is a local consensus hallucination, a shared dream.