noun en·mi·ty \ˈen-mə-tē\
1 : positive, active, and typically mutual hatred or ill will
Origin of ENMITY
Middle English enmite, from Anglo-French enemité, enemisté, from enemi enemy
First Known Use: 13th century
This word is used in the Bible, and I came across it in my studies the other day. To be at enmity with someone is to be at odds with them. The use of the word "hatred" in the Merriam-Webster definition above would seem to be a bit harsher than I would normally attribute to this word.
Another definition would be: the state or feeling of being actively opposed or hostile to someone or something.
That is more in line with what I intend when I use this word.