I have my own ideas about what "spirit" means, which is a different subject and context to the thread. Somebody mentioned being created in the image of God, and somebody else commented about God having a physical body.
Since I am in no way an ancient Hebrew, Aramaic or Greek scholar, nor am I an expert in the culture and times of the writings of the Bible, I cannot say what the writers might have meant by the word "spirit", other than guess with my western perspective. Anyone can look for themselves if they're so interested.
"Spirit" isn't matter. It isn't energy. So say those who claim to know such things. In other words, it isn't anything we know. Nor is it anything the "experts" know. I suspect therefore that it's nothing at all. [Always subject to the presentation of varifiable evidence, of course.]