A webcast is a live or pre-recorded audio and/or video broadcast that is delivered over the internet. It allows people to watch or listen to content from their computers, smartphones, or other devices connected to the internet.
Usage examples
The company organized a webcast to announce their new product launch to a global audience.
The university is conducting a webcast of the guest lecture so that students from other campuses can participate.
The music festival decided to webcast the performances online for fans who couldn't attend the event.
I've written here and here about the Massachusetts Supreme Judicial Court's launch last spring of live webcasts of its oral arguments. (lawsitesblog.com)
TCTV.live hosts live webcasts of therapy sessions (and live supervision of these sessions!) (tctv.live)
On May 16, 2014 the Copyright Board released its decision certifying Re: Sound Tariff 8 setting royalty rates for webcasting services in Canada. (slaw.ca)