Joti Jot (Meaning: immersed in the Eternal Light). The Guru's and holy Sikh scriptures teach that if someone is immortal (or attained immortality during the course of their life), when they leave this existence they have not died. They have rejoined with God. As someone who is immortal cannot die. This special condition is given the word Joti Jot.
References
Joti Jot Wikipedia(Text) CC BY-SA