A weathercaster is the person who presents the weather on television or radio — the one standing in front of the map telling you a typhoon is coming. It is made from "weather" plus the "-caster" of "broadcaster", exactly the way "newscaster" and "sportscaster" are made. The word is mainly American, and it is chiefly a media-industry word: it appears in job listings, TV station websites, and articles about broadcasting. Ordinary people watching at home say "the weather guy", "the weather lady", or in Britain "the weather forecaster". So treat it as a term you should recognise when you read it, not one you need in daily speech. Its real usefulness is that it does not say whether the person is a man or a woman. The older words "weatherman" and "weather girl" both do, and "weather girl" carries an unpleasant history — it was used in the 1960s and 70s for young women hired to look pretty while reading a forecast someone else prepared. Many stations now avoid it, and a woman doing this job today would rather be called a weathercaster, a weather presenter, or a meteorologist. Your dictionary defines this word by those two older words, so it is worth knowing what has changed around them. One more distinction: a weathercaster is not automatically a meteorologist. A meteorologist has studied the science; a weathercaster presents the forecast, and may or may not have that training. American stations advertise "certified" weathercasters for exactly this reason.

氣象主播、天氣播報員（美式用法，多見於媒體業內；台灣觀眾平常就說「氣象主播」。優點是不分男女，比舊詞 weatherman／weather girl 得體）