A rant refers to a passionate speech or piece of writing that expresses strong emotions, usually in a critical or complaining manner. It is often characterized by its length and intensity. In the context of the clue, rants would refer to lengthy Facebook posts that express strong opinions or grievances.
Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Posts in a rage, perhaps. Explanations are generated by AI and may be inaccurate.