Has anybody ever used this acronym IHY around or directly for you and you felt not affected, I'm afraid what your next step would be after knowing what the slang stands for? IHY is the acronym for I Hate You. It is a very common slang, describing how you passionately dislike someone.
When you don't like someone's attitude, behavior or character, the common expression that people tend to use is 'I hate you', but at times when the word is used to describe you, it doesn't mean people really hate you, some people do play with it.
For example you might decide to fool someone and the person fell for it, that person might tell you IHY and that doesn't mean he truly hates you. Slang like this is something very common on social media. People use it when chatting with their friends. It can be used anyhow in a sentence but be careful not to use it in formal communication or writing.