What's a spirit?

Via Shamanism.org:

In 1961, when I was with the Conibo Indians in eastern Peru in the Amazon, I was training using ayahuasca with a shaman, and we were working with the various nature spirits every night. I worked with the anaconda spirit, the black panther spirit, the fresh-water dolphin spirit, various tree spirits, and so on. They would come, we would see them, and so on. Then one night I got introduced to the outboard-motor spirit. And then the radio spirit and the airplane spirit. I came to realize that anything that you see in complete darkness or with your eyes closed is technically a spirit. That makes it sound like it’s just an image in the air, but shamans find out which spirits have power and which don’t. They discover what spirits can help in what ways. It’s very important to recognize that whatever you contact in nonordinary reality is technically a spirit. It’s a spiritual reality.