Webcasting is sending video or sound out over the internet so that many people can watch or listen at the same time — a company's yearly meeting, a concert, a school ceremony, a religious service, a news event. The idea comes straight from broadcasting: a radio or TV station 'broadcasts' to everyone at once, and a webcast does the same thing through the web instead of through the air. Honestly, this word sounds a bit dated now. It belongs to the 2000s, when putting live video on the internet was still special enough to need its own name. Today most people say livestreaming, going live, or just 'streaming it'. Where webcast survives is formal, corporate and institutional language: an investor webcast, a webcast of the conference, 'the lecture will be webcast live'. If you see it on a company website, that is exactly the flavour. One fine point that separates it from streaming in general: a webcast is usually one-to-many and scheduled — it happens at a time, and everyone joins to watch the same thing. It is not a video you click whenever you like, and it is not a two-way meeting where everyone talks. Watching, not chatting. The forms: webcast is both the noun (a webcast) and the verb (to webcast something); webcasting is the activity itself.

網路直播、線上轉播（一對多、有時間的那種）。台灣現在日常都講「直播」；webcast 這個字偏正式，多用在法說會、研討會、典禮的線上轉播。