"Reaction videos" refer to videos where people film their genuine and immediate responses to watching or experiencing something, such as a new movie, TV show, or viral video. Full definition
We're going to have video feeds, live blogs, and reaction videos for every single one of the show's big conferences! (shortpause.com)
Nevertheless, it's easily one of the best reaction videos online. (techtimes.com)
They have attempted to trademark a generic word like «react» and tried to claim other people's content... Even those that did reaction videos well before they did. (gonintendo.com)