Gilgul'im neshamot (jewish concept of reincarnation) literally means 'circles of the souls' (around lifes or incarnations to the body). This is deep secret of nature explained in kabbalah. Lowest part of the soul - neshama is always a gilgul, like a default life spark of any living body.
Classic kabbalah work Shaar ha Gilgulim ("Gate of Reincarnations") of Arizal or Isaac Luria, (written by his disciple Chaim Vital), describes these amazing, deep & very complex laws of reincarnation and impregnation ("pregnancy") ibbur of 5 different parts of the soul.
Gilgul or gilgulneshamot or Gilgul'im neshamot refers to the concept of reincarnation within the Kabbalah of Judaism.
in Hebrew, the word gilgul means "cycles" or "circles" and neshamot is the plural for "souls" of souls which are "cycled" through "lives or "incarnations" into the body.
The lowest part of the soul which is called the neshama is always a gilgul, like a "default life spark" within any living body.