What Does A Black Shadow Mean?

A black shadow is usually considered to be the presence of an evil spirit. Some people don't believe in evil spirits but readily believe in angels.
If you have a gut feeling about this shadow, listen to your instincts. That's what they are programmed into you for.
Does the enmity make you feel afraid or apprehensive? If so, it is evil.
Do you have a good feeling when you see it and a feeling of calm? If so, then I wouldn't be concerned about it.
But if it is the bad feeling, then I would recommend that you take some olive oil and ask God to bless it. Then put a dab of the oil over each entryway of your home, "Including windows", then tell the spirit to leave in the name of Jesus Christ. Then, speak blessings upon and only good to enter into your house from that time on.
This is only my opinion. Some people are not aware of matters concerning the spirit world because they choose not to believe in it. Others simply have no knowledge of or do not believe in the written word of the Bible.
Ultimately, it's your call.
I'll probably catch some flack over this answer, but thought I'd put it out there anyway.  ♀

According to the ole' lady Depending on the feeling that you get when you walk into the house whether you are scared or ok with it, If you are ok with it then you just have a "guest" in your house. If not then there is a clensing you can do that involves sage and or sweet grass, a white candle, and a small saying. "I clense this house in the name of all any good energy may stay, All negative energy must go, this is my will so mote it be." Start in the back of your house and walk the candle and sage(sweet grass) clockwise throughout your house. After you do this let the candle burn out on its own, Do not blow it out.