SO Meaning in Chat or Text Messages Online

In internet slang, "SO" stands for "Significant Other". It is generally used to refer to a person's romantic partner, whether they are in a committed relationship or not. To use it in a sentence, you might say "I'm going out to dinner with my SO tonight" or "My SO and I have been together for four years now". This term is often used to avoid using gendered language like "boyfriend" or "girlfriend" and can be inclusive of any type of romantic relationship.