A mirrorless interchangeable-lens camera (MILC) is exactly what the Leica M9 is. The principle attribute of a MILC is that there is no mirror in the lens to sensor path. The M9 does lack features that are available in most other MILC systems however, IMHO, still qualifies as part of this genre of cameras.
Not quite. The principle attribute of a MILC is that there is no mirror in the lens to sensor path
so that the sensor serves all functions of metering, auto focus, image framing and image capture. That's what all mirrorless cameras have in common. That's obviously not the case with an M9 rangefinder...which is why we all refer to the M9 as a rangefinder, not as a mirrorless camera. Yes, in a rangefinder there is no mirror in path of the sensor, but the sensor is totally blind and inactive the whole time except for the moment you take a photo. That's not the case with MILCs. MILCs have no mirror in the path of the sensor specifically so that the sensor can carry out the duties of metering, auto focus, image framing and image capture. A rangefinder is fundamentally different, which is why rangefinders are called rangefinders, not MILCs. The only people who refer to rangefinders as MILCs are doing it erroneously. Plus, there is that small issue of rangefinders having mirrors, which makes it hard to call them "mirrorless"