Well, the word mirrorless implies for me most of all, that it doesn't have a mirror, in contrast to a (D)SLR. Of course, most of the time, mirrorless is used for cameras which have exchangeable lenses and an electronic viewfinder. That is, why I explicitly stated in my post, that while not having a mirror, the M9 didn't have an EVF.

The M(240) then added the EVF, which also precedes the A7.

All of this is a bit of trivia, as most people are not aware of the Leica M series, so I thought it would add to the discussion. The A7 certainly was the first EVF-only mirrorless 35mm camera and was sold in far higher numbers than any digital M.