The phrase "official livestream" means a real-time video or broadcast that is officially authorized and sanctioned by a particular organization or person. Full definition
During a recent official livestream (via Nintendo Everything), the company hinted that news will be coming very soon. (flipboard.com)
If you're interested in seeing more of the game, make sure to check out the official livestream from 6PM CET / 5PM GMT to 8PM CET / 7PM GMT on Twitch! (perfectly-nintendo.com)
Recently, in an official livestream, SEGA PR representative Aaron Webber had some news to share on... (nintendoenthusiast.com)