means a person who uses magick strictly for the purpose of bewitching (kuroya) another individual or even a group of people whom they don't like with an intense passion courtesy of deep-rooted demonic-driven envy.
And in the process of wreaking havoc, they may use either mbashto, chikwambo, zvidhoma, etc. Sometimes they can go as far as using natural elemental forces such as mheni (thunder-lightning bolt) in broad daylight to strike the next person dead.
The plural for muroyi is varoyi.
Note: besides acts of Satanic witchcraft (huroyi), the word muroyi is also used to describe a "hater" i.e. a person who is envious of your success in life. So much that they will relentlessly find ways to orchestrate your downfall with every chance they get; however, without doing it spiritually e.g. the use of spells, etc.