A weatherman is the man you see on TV (or hear on the radio) who tells you the weather — today it will rain, tomorrow will be hot, a typhoon is coming. He stands in front of a map and points. The word is a compound of the plainest kind: the man who does the weather.

Two things about it are worth knowing. First, it is an everyday word, not a job title on a name card. The person's real job might be 'meteorologist' — a scientist who studies weather — or they might just be a presenter reading what the scientists wrote. 'Weatherman' covers both, because from the sofa you cannot tell the difference. If you want to sound formal, say meteorologist. If you are talking to a friend, weatherman.

Second, the -man part. Many weather presenters are women, and 'weatherwoman' does exist, but a lot of people now avoid the whole -man/-woman question and say 'weather presenter', 'weather reporter', or 'weather forecaster' instead. Older speakers still say weatherman for anyone. Younger speakers and news companies often do not. Neither is wrong; they come from different years.

People also use it as a small joke about being wrong. 'Nobody believes the weatherman' is a thing English speakers say, because forecasts miss. There is a famous song line — 'you don't need a weatherman to know which way the wind blows' — which means: this is so obvious you don't need an expert to tell you.