It seems to me that our definition of consciousness is just our own state of mind. A scale that starts with our own individual sense of consciousness (most conscious) and goes to infinite (least conscious).
Do we believe there is anything more conscious then our own individual self at the current moment in time?
The more similar we perceive and empathize with another entity the more conscious we believe them to be.
But I think in a practical sense it doesn't matter too much. Theres no global hierarchy of consciousness.
A rock isn't very similar to us. But once that rocks starts talking/communicating with us enough that we can empathize with it and think that it understands us. We will call it conscious and probably give it the rights we think it deserves.