Killing Intent is simply the user exuding pure killing intention, and having it affect their opponent, themselves, and others around them, up to the point of paralysing them with fear. When the Killing Intent is particularly strong, it can even give the victim visions of their own gruesome death. This can cause killing intent to be confused with a genjutsu, despite it not being a technique at all.
Sakki (殺気) can also be translated to "thirst for blood".
The Naruto fandom has labelled the technique "Death Foreseeing Technique" (死の観覧の術, Shikumi no Jutsu). It should be noted that the kanji and rōmaji do not match up and neither mean "Death Foreseeing Technique". The kanji used (死の観覧の術) would be pronounced as "shi no kanran no jutsu" and mean "death viewing technique". The rōmaji used (Shikumi no Jutsu) would mean something like "death assembling technique" (死組みの術).