It means there's something you have absolutely no awareness of. You can't see it, taste it, smell it, touch it, hear it or sense it. It's as though it does not exist whatsoever. And since you place a lot of trust in your body's perceptual abilities you conclude that whatever is unconscious simply does not exist. That's the whole point of having made something unconscious in the first place.
For you, what you consider sanity, and what you consider to make sense, and who you think you are, are all based on how much awareness you have. You believe that you are fully aware right now of everything there is to be aware of.
Your sense of identity is intimately tied into this, because the edges of your awareness of Self creates a sense of where you stop and where otherness begins. Anything outside of your self seems to be not who you are.
The problem is that it's possible for there to be something so out of your awareness, so inaccessible to your senses, that you have absolutely no evidence of it and absolutely no way to believe that it's there. It'd be like me telling you there's a giant pink monster dancing outside your house, and without you being able to see it whatsoever you have absolutely no reason to believe me.
You do place a lot of trust in what your body shows you and if you cannot perceive something, you basically will say, well.... that doesn't exist, it's not true. And if someone else is experiencing something that seems totally unreal and untrue for you, you will not believe them, and dismiss it as fictional nonsense.
But it is actually possible for there to be something that exists outside of your conscious awareness. It's actually there, but you seem to have absolutely no awareness of it. This relates not only to immense unconscious guilt and unconscious sin, but also to the presence of God. You have made God unconscious to you, and in being not aware of His presence you basically believe that He does not exist.
While you are unconscious of God, or other stuff, it's possible for your mind to conceive of what might be there, to develop trust that it is there, and to utilize it in some way or experience/witness its expressions, without you necessarily being able to be fully aware of it, to understand it, to directly experience it or to see it. Placing some amount of belief in its existence, even if it is outside of awareness, is an act of "faith", ie trusting in something you believe is true in order to bridge the gap between your limited awareness and a state of greater awareness which is temporarily hidden.
As A Course in Miracles says: "The miracle is taken first on faith, because to ask for it implies the mind has been made ready to conceive of what it cannot see and does not understand. Yet faith will bring its witnesses to show that what it rested on is really there. And thus the miracle will justify your faith in it, and show it rested on a world more real than what you saw before; a world redeemed from what you thought was there."
As Jesus is telling us, it is possible to have faith in God and trust God's truth, to some extent, even if you're not fully experiencing Him yet. You might not be in a state of revelation, but miracles pave the way for revelation. This also means that it is possible to receive the benefits or expressions of that love, even if it's coming from outside your awareness, and to SEE (ie witness) its power and effects in the form of miracles, even if you do not yet understand it.
Such miracles don't require you to be fully aware of God. They only require you to trust and therefore have faith that God is there to do His part and fulfill His function at all times, regardless of your readiness or willingness, and all it takes is a LITTLE willingness from you to open the door and let Him in. This includes the correction/healing of your mind but it also includes the expression of love as miracles of healing and other manifestations, which can come about through having faith/trust even if you are not yet aware of the whole of yourself as Christ.
At some point we will cease to be unconscious and therefore will cease to be limited. We will be more directly able to express love and use its power. Until then, we learn to trust in a power greater than what we are aware of, even if we can't see it, and gradually the gap between you and it will diminish, it will reveal itself more directly over time as love's presence, and you will eventually be One with it, recognizing yourself in it.