BKB / Black King Bar:

BKB, short for Black King Bar, is a Dota 2 item that grants temporary spell immunity, letting the holder ignore many enemy disables and damage spells. It is most often used by core heroes to commit to fights, channel important abilities, or survive burst damage while moving through enemy control. Because many effects still work through it, BKB is best understood as a tool for reducing magical interruption rather than a complete defense.