PLAGIARISM is the wrongful appropriation and stealing and publication of another author's "language, thoughts, ideas, or expressions" and the representation of them as one's own original work. (From Wikipedia, The Free Encyclopedia)
I believe we have all seen on Steemit pictures, videos, written content, etc. that probably was not the property of the persons posting them but was copied off of someone else's internet site or other source without permission. Such plagiarism can get you in trouble. It is also copyright infringement if the work in question has been copyrighted. Then it may be considered a crime.
I was told by a local very high end rare book dealer that he personally knew a rare book dealer that sold on ebay who would sue in civil court if you cut and pasted or otherwise copied his detailed descriptions and / or photos of books that he was selling there and used that info to sell your own books. He gave you one warning, but if you copied him a second time he would sue you in court. Money was no problem to him. He successfully sued for $3000 at least once. You don't want a guy like this after you. And you don't want him complaining to Steemit.