预告 (yùgào) means 'to announce in advance' or 'preview/trailer' — it's the word for a public notice or promotional preview (e.g., a movie trailer or product teaser). Unlike 预报 (yùbào, weather/event forecast) or 预测 (yùcè, data-based prediction), 预告 focuses on announcing something that will happen, often with media or event context. As a noun, it specifically refers to a preview or trailer.