From David Ocker:

"I remember asking Frank [Zappa] what the title meant. He said "While You Were Out" referred to someone who had gotten out of prison - I had the impression it was someone specific, but I'm not sure who. (ASIDE: Another time someone asked Frank what had happened to the other members of his first band in San Diego - "In prison" was his instant reply.) At some point the title was changed to "While You Were Art" - this had a double meaning - it referred to Art Jarvinen himself, who was motivating the project and acting as go-between between Frank and the ensemble - several of whom had to be convinced to go along with this project. "ART" also referred, I think, to the "ART" in worlds like "Art-world", "Art-music" or"High-art" - in other words, Frank was using it as a term of derision."