Sermonising, which means giving a lecture or preaching in a moralistic and superior way, has a few different synonyms that can be used interchangeably. First, the word pontificating can be used. It suggests a similar tone as sermonising, where the speaker is giving advice or a lecture in a condescending way. Another synonym for sermonising is moralizing. This word implies that the speaker is offering moral guidance and lessons in a preachy manner. Additionally, lecturing is a synonym that might fit in the right context, with the connotation of providing information in a formal and possibly boring way. Lastly, admonishing is another synonym that could be used when a speaker is reprimanding or warning with a tone of moral superiority.