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.