Am sure most of us know Satan has an evil spirit that goes about tormenting people it wants to torment.
In the Bible Satan is said to be an Archangel of God who was dropped down to earth from heaven by God because he was trying to take the place of God.
To know more about the history of Satan has described in the Bible, you can check this verses, Isaiah 14:12-15, Ezekiel 28:12-19.
So yes, it is true that Satan is a religious word, but I can tell you that Satan is not just religious word and an evil spirit going about tormenting people it wants to torment. I think the English language has limited the meaning of Satan to just mean a religious word [an evil spirit].
But Satan and the word Satan is more than just an evil spirit, it is a Hebrew word and in Hebrew it means adversary. So literally anybody strongly opposing you, sabotaging you, whether man or spirit is Satan. And so the word Satan is a secular word, but it is used more in religion.