Woodworking

I would think it specifically excludes aggregate or laminated products like MDF, OSB, or plywood.

It is lumber sawn whole from the tree.

not mdf, not plywood, solid tree, no glues.

Solid wood has the same grain texture all the way through. Plywood, MDF, OSB, etc., are engineered wood. Basically, if it says 'solid wood,' my assumption is that what I see is what I get. If it’s plywood with a hardwood veneer, then it’s trying to trick me into thinking it’s something it’s not, and that doesn’t count. Although, technically, if a piece is made of plywood and doesn’t try to hide it, I guess you could argue it’s solid wood - because, technically, it is.

Something is "solid wood" if it's made from pieces of solid-sawn lumber. If it's built up from rotary-peeled veneers, woodchips, sawdust, or pulp, then it is not solid wood.

If it's on a product like a piece of furniture, then it means any part not specifically labeled as "solid wood" is some sort of composite material.

e.g. "solid wood table top!" = legs and frame are made of the cheapest shit we could find

These are all great definitions.
A hard erection is another interpretation.

Cardboard's out.

Solid wood is generally understood to be lumber or timber, that is pieces of wood sawn from a tree. This is distinct from engineered wood or manufactured wood products which include MDF, plywood, and OSB. Engineered wood is made of fibers or strands that are pressed or glued, there is more in the final stock than just wood (I.e., glue, lignin separated via heating and pressing).

Particle board ~~and plywood~~ is made of sawdust and wood shavings. My definition of solid wood is something that came directly from a tree with the only major processing being cutting it into board, sheet, or similar.

The wood is continuous, from a single tree, from one surface to the other.*

*Veneer is ok I guess, but I would rather see a cheap real surface than an expensive sheet of paper.

I think someone is making an inappropriate joke

In almost all contexts, "solid wood" means a piece of a tree cut to shape. No engineered wood products to include plywood, OSB, particle board/pressboard/chipboard, MDF, glulam, etc. I will make allowances for shop-made laminations as you might do when edge gluind panels, gluing up boards to make thicker posts than are available, or to ease bending/forming.

I have a suspicion and this comment section is confirming that. I briefly worked putting places together for short term rentals. Sometimes I had to put together IKEA furniture, other times it was "real wood" furniture. As in, the label claimed it was real wood. This "real wood" however always looked suspicious to me. The feel wasn't there, the grain was barely convincing, no mention of any species, some "mistakes" seemed odd such as a random saw cut in an otherwise well finished piece. They were always manufactured somewhere in SEA. My guess is "real wood" has no clear definition as evidenced in this comment section and some people see it as an interchangeable term for good quality. So manufacturers can design something that looks like a solid white oak bench and charge premium for it. After all they've made no promises. If it were for instance engineered out of bamboo, it is in fact real wood Or can be defended as such.