Asked whether it could be categorised as folk, rock or pop, she replied: "I don't know what it is. You heard it. What kind of music is it?"
Not Commercial, released on her official website on Wednesday, was recorded in 1994 on a shoestring budget when she was between record deals.
After it was rejected by a senior UK record industry figure, it lay "in a little safe" at home for six years, until a friend suggested she could use her website to sell it.
But now her die-hard fans can log on and order it - even though she says: "I'm not even sure it's any good."
She told US music website Wall of Sound: "I do think it will be meaningful to a few people. It's like some strange hybrid of music. Like stories sung to you."
Asked whether it could be categorised as folk, rock or pop, she replied: "I don't know what it is. You heard it. What kind of music is it?"
The album was written after Cher - who does not normally write her own lyrics - attended a songwriters' conference.
It deals with her unhappy childhood, the Catholic Church, the suicide that year of Nirvana singer Kurt Cobain and a relationship with a married man.
Despite the illuminating nature of the album, Warner Music UK boss Rob Dickens - a friend of the singer and now the head of the British Phonographic Industry - rejected the album as "nice, but not commercial".
She went on to make two albums - including 1998's Believe - for Warner, and is making a third now, due for release in 2001.
However, she is determined that Not Commercial will be a low-key release.
"I don't see this as being a very big album. I won't be playing it anywhere," she said.
"I was listening to it the other day and I thought this stuff is so personal, is anyone gonna give a s**t?"