to tell people about a particular religion, way of life, system, etc. in order to persuade them to accept it 宣传，宣扬，宣讲（教义、生活方式、体制等）
to give sb advice on moral standards, behaviour, etc., especially in a way that they find annoying or boring 说教
I’m sorry, I didn’t mean to preach.
很抱歉，我并没有说教的意思。
~ at sb
You’re preaching at me again!
你又在对我说教了！