Pirsig offers this definition:
"Quality is a characteristic of thought and statement that is
recognized by a nonthinking process. Because definitions are a
product of rigid, formal thinking, quality cannot be defined."
..."When I say, 'Quality cannot be defined,' I'm really saying
formally, 'I'm stupic about Quality."
...But then below the definition on the blackboard, he wrote, "But
even though Quality cannot be defined, you know what Quality is..."
You can actually search the text of the book by using the 'Inside the
Book' feature at Amazon.com:
The above excerpt is taken from pages 184-185 of the online text.
Let me know if there's anything else you need on this.