Everybody know what "landscape" is?
Of course. "Landscape" is wider than high, and "portrait" is higher than wide. The other classic shapes are square, round, and oval.

I'm all in favor of genre-free threads. The potential value to some viewers of "Landscape" or "Street" Showcases is that it makes it easy to avoid genres they don't care for. But for me that is a non-issue, as I like to check on all posted images of any sort, even ones that I do very little of, such as "Street" (because it is very difficult to do well.) I do find that I respond more positively to those that fit the "classic" definition that Russ has described so well so often.
But I find quite boring the repeated queries about "Is this (pick a genre)?" I like to read comments that might make an image more expressive, and ones that assert no changes are desirable. I also skip all the political and quasi-scientific discussions, preferring the threads with actual photographs (plus, of course, the Humor thread.)
YMMV.