刷 (shuā) literally 'to brush/swipe', but slangily means 'to do something repeatedly/in bulk' —
刷视频 (binge short videos),
刷剧 (binge a show),
刷弹幕 (spam bullet comments),
刷礼物 (rapid-fire gifting).
礼物 here are virtual icons (rockets, sports cars, castles) viewers buy and 'send' on screen during live broadcasts.