What is the meaning of the idiom "No love lost"?

The idiom "no love lost" means not on good terms. It is used to describe two people or groups who do not like each other at all. For example, you might say "There's no love lost between those two politicians."

The other options are not correct. "On good terms" means that two people or groups have a friendly or cordial relationship. "Forming a group" means coming together to achieve a common goal. "Stop loving" means to no longer have feelings of love for someone.